v3.25.2
Schedules of Investments and Advances to Affiliates (Details) - USD ($)
6 Months Ended 12 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2024
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [1],[2],[3] $ 3,966,075,000    
Fair value, ending balance 4,083,453,000 [4],[5],[6]   $ 3,966,075,000 [1],[2],[3]
Net change in deferred taxes (3,731,000) $ (1,029,000) (2,100,000)
Total Control Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 40,275,000   84,728,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 785,556,000 68,100,000 68,100,000
Gross additions 67,888,000   762,372,000
Gross reductions (127,030,000)   (30,175,000)
Realized Gain/(Loss) (164,000)   (8,000)
Change in Unrealized Gain (Loss) (11,392,000)   (14,734,000)
Fair value, ending balance 714,858,000   785,556,000
Affiliated      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 1,649,000   5,814,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 35,596,000 0 0
Gross additions 13,012,000   53,513,000
Gross reductions (4,164,000)   (16,355,000)
Realized Gain/(Loss) 137,000   565,000
Change in Unrealized Gain (Loss) (2,511,000)   (2,127,000)
Fair value, ending balance 42,070,000   35,596,000
Total Control & Affiliate Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 41,924,000   90,542,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 821,152,000 68,100,000 68,100,000
Gross additions 80,900,000   815,885,000
Gross reductions (131,194,000)   (46,530,000)
Realized Gain/(Loss) (27,000)   557,000
Change in Unrealized Gain (Loss) (13,903,000)   (16,861,000)
Fair value, ending balance 756,928,000   821,152,000
Investment, Affiliated Issuer, No Longer Held      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 500    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Realized Gain/(Loss) 136,600    
Change in Unrealized Gain (Loss) (140,100)    
Investment, Identifier [Axis]: 1236904 BC, Ltd., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 14,332,000    
Investment, Identifier [Axis]: 1236904 BC, Ltd., Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 14,846,000    
Fair value, ending balance 17,022,000 [7],[8],[11]   14,846,000 [9],[10]
Investment, Identifier [Axis]: 1236904 BC, Ltd., Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 17,431,000    
Fair value, ending balance [9],[10],[12]     17,431,000
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC , Healthcare 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 3,845,000    
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC , Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 123,000    
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC , Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 141,000    
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC , Healthcare 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 18,756,000    
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC, Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 124,000    
Fair value, ending balance [10]     124,000
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC, Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 141,000    
Fair value, ending balance [10],[14]     141,000
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC, Healthcare 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 3,865,000    
Fair value, ending balance [9],[10]     3,865,000
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC, Healthcare 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 18,854,000    
Fair value, ending balance [9],[10]     18,854,000
Investment, Identifier [Axis]: AIG CLO, Ltd. 21-1A F, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,287,000    
Fair value, ending balance 1,320,000   1,287,000
Investment, Identifier [Axis]: AP Gaming I, LLC , Gaming/Lodging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,114,000    
Fair value, ending balance     7,114,000
Investment, Identifier [Axis]: ARC Falcon I, Inc., Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,999,000    
Investment, Identifier [Axis]: Accel International Holdings, LLC , Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (23,000)    
Investment, Identifier [Axis]: Accel International Holdings, LLC , Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 27,549,000    
Investment, Identifier [Axis]: Acrisure, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 17,223,000    
Fair value, ending balance     17,223,000
Investment, Identifier [Axis]: Acrisure, LLC / Finance, Inc., Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,798,000    
Investment, Identifier [Axis]: Acrisure, LLC, Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 7,178,000    
Investment, Identifier [Axis]: Adelaide Borrower, LLC , Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: Adelaide Borrower, LLC , Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: Adelaide Borrower, LLC , Software/Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 35,285,000    
Investment, Identifier [Axis]: Adelaide Borrower, LLC, Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 34,652,000    
Fair value, ending balance [9],[10],[12]     34,652,000
Investment, Identifier [Axis]: Adelaide Borrower, LLC, Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (142,000)    
Fair value, ending balance [10],[14]     (142,000)
Investment, Identifier [Axis]: Adelaide Borrower, LLC, Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (89,000)    
Fair value, ending balance [10],[14]     (89,000)
Investment, Identifier [Axis]: Adtalem Global Education, Inc. , Education 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 585,000    
Fair value, ending balance     585,000
Investment, Identifier [Axis]: Adtalem Global Education, Inc. , Education 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,020,000    
Fair value, ending balance     1,020,000
Investment, Identifier [Axis]: Adtalem Global Education, Inc., Education      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 353,000    
Investment, Identifier [Axis]: Air Canada, Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,861,000    
Fair value, ending balance 1,980,000   4,861,000
Investment, Identifier [Axis]: Albion Financing 3 SARL , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,076,000    
Fair value, ending balance 3,037,000   3,076,000
Investment, Identifier [Axis]: Alera Group Intermediate Holdings, Inc., Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 4,686,000    
Fair value, ending balance [10],[14]     4,686,000
Investment, Identifier [Axis]: Alera Group Intermediate Holdings, Inc., Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 8,609,000    
Fair value, ending balance [9],[10]     8,609,000
Investment, Identifier [Axis]: Alera Group Intermediate Holdings, Inc., Financials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 17,267,000    
Fair value, ending balance [9],[10]     17,267,000
Investment, Identifier [Axis]: Alera Group, Inc. , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[11] 22,598,000    
Investment, Identifier [Axis]: Alera Group, Inc., Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 7,801,000    
Investment, Identifier [Axis]: Alliant Holdings Intermediate, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,995,000    
Fair value, ending balance     4,995,000
Investment, Identifier [Axis]: Alpha Generation, LLC, Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,311,000    
Fair value, ending balance     5,311,000
Investment, Identifier [Axis]: Altice Financing, SA , Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,565,000    
Fair value, ending balance     1,565,000
Investment, Identifier [Axis]: Altice France, SA , Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,880,000    
Fair value, ending balance     9,880,000
Investment, Identifier [Axis]: Alvogen Pharma US, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,692,000    
Fair value, ending balance 578,000   9,692,000
Investment, Identifier [Axis]: Amentum Government Services Holdings, LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 8,536,000    
Fair value, ending balance     8,536,000
Investment, Identifier [Axis]: American Airlines Inc/AAdvantage Loyalty IP, Ltd., Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,575,000    
Fair value, ending balance     4,575,000
Investment, Identifier [Axis]: American Builders & Contractors Supply Co., Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,909,000    
Fair value, ending balance     1,909,000
Investment, Identifier [Axis]: American Rock Salt Company, LLC , Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 5,411,000    
Fair value, ending balance [9],[10]     5,411,000
Investment, Identifier [Axis]: American Rock Salt Company, LLC, Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9] 1,796,000    
Fair value, ending balance 1,612,000 [7]   1,796,000 [9]
Investment, Identifier [Axis]: American Rock Salt Company, LLC, Chemicals 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,749,000    
Fair value, ending balance 5,238,000 [7],[8]   1,749,000
Investment, Identifier [Axis]: American Rock Salt Company, LLC, Chemicals 1.1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 1,693,000    
Investment, Identifier [Axis]: Amylu Borrower Sub, LLC , Food & Beverage 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (67,000)    
Investment, Identifier [Axis]: Amylu Borrower Sub, LLC, Food & Beverage 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 486,000    
Investment, Identifier [Axis]: Amylu Borrower Sub, LLC, Food & Beverage 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 39,142,000    
Investment, Identifier [Axis]: Anchor Glass Container Corp., Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[15] 2,921,000    
Fair value, ending balance 3,124,000 [8],[16]   2,921,000 [10],[15]
Investment, Identifier [Axis]: Apollo Commercial Real Estate Finance, Inc. , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,599,000    
Fair value, ending balance     2,599,000
Investment, Identifier [Axis]: Apollo Commercial Real Estate Finance, Inc., Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,847,000    
Investment, Identifier [Axis]: Arch Global Precision, LLC , Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 2,308,000    
Fair value, ending balance 2,296,000 [8]   2,308,000 [10]
Investment, Identifier [Axis]: Arch Global Precision, LLC , Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 901,000    
Investment, Identifier [Axis]: Arch Global Precision, LLC , Industrials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 7,288,000    
Investment, Identifier [Axis]: Arch Global Precision, LLC, Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 992,000    
Fair value, ending balance [10],[14]     992,000
Investment, Identifier [Axis]: Arch Global Precision, LLC, Industrials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 7,326,000    
Fair value, ending balance [9],[10],[12]     7,326,000
Investment, Identifier [Axis]: Arches Buyer, Inc. , Publishing      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,829,000    
Fair value, ending balance 5,866,000   5,829,000
Investment, Identifier [Axis]: Arcline FM Holdings, LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 5,020,000    
Investment, Identifier [Axis]: Arcosa, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,309,000    
Fair value, ending balance     1,309,000
Investment, Identifier [Axis]: Arctic Holdco, LLC , Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 3,926,000    
Fair value, ending balance [10],[14]     3,926,000
Investment, Identifier [Axis]: Arctic Holdco, LLC , Paper & Packaging 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 59,404,000    
Fair value, ending balance 3,210,000 [8],[13]   59,404,000 [9],[10],[12]
Investment, Identifier [Axis]: Arctic Holdco, LLC , Paper & Packaging 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 1,232,000    
Investment, Identifier [Axis]: Arctic Holdco, LLC , Paper & Packaging 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 45,720,000    
Investment, Identifier [Axis]: Armada Parent, Inc, Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[14] 3,203,000    
Fair value, ending balance [9],[10],[14]     3,203,000
Investment, Identifier [Axis]: Armada Parent, Inc. , Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 1,618,000    
Investment, Identifier [Axis]: Armada Parent, Inc. , Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 63,569,000    
Fair value, ending balance [9],[10]     63,569,000
Investment, Identifier [Axis]: Armada Parent, Inc. , Industrials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 55,500,000    
Investment, Identifier [Axis]: Armada Parent, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: Armada Parent, Inc., Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (19,000)    
Investment, Identifier [Axis]: Artera Services, LLC , Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,519,000    
Fair value, ending balance 4,627,000   5,519,000
Investment, Identifier [Axis]: Artifact Bidco, Inc. Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (18,000)    
Fair value, ending balance [10],[14]     (18,000)
Investment, Identifier [Axis]: Artifact Bidco, Inc., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 10,773,000    
Fair value, ending balance [9],[10],[12]     10,773,000
Investment, Identifier [Axis]: Artifact Bidco, Inc., Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (25,000)    
Fair value, ending balance 0 [8],[13]   (25,000) [10],[14]
Investment, Identifier [Axis]: Artifact Bidco, Inc., Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: Artifact Bidco, Inc., Software/Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 10,875,000    
Investment, Identifier [Axis]: Aruba Investments Holdings, LLC, Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[12] 3,604,000    
Fair value, ending balance 3,604,000 [8],[11]   3,604,000 [10],[12]
Investment, Identifier [Axis]: Ascend Learning, LLC , Education      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 1,994,000    
Investment, Identifier [Axis]: Ascensus Group Holdings, Inc. , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,601,000    
Fair value, ending balance 7,512,000   7,601,000
Investment, Identifier [Axis]: Astoria Energy, LLC , Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,733,000    
Fair value, ending balance     1,733,000
Investment, Identifier [Axis]: Asurion, LLC , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,012,000    
Fair value, ending balance     4,012,000
Investment, Identifier [Axis]: Athenahealth Group, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 12,704,000    
Fair value, ending balance 9,959,000   12,704,000
Investment, Identifier [Axis]: Athletico Management, LLC Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,739,000    
Fair value, ending balance     3,739,000
Investment, Identifier [Axis]: Athletico Management, LLC , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 3,296,000    
Investment, Identifier [Axis]: AuditBoard, Inc. , Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 22,887,000    
Investment, Identifier [Axis]: AuditBoard, Inc. , Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: AuditBoard, Inc. , Software/Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: AuditBoard, Inc., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 22,674,000    
Fair value, ending balance [10]     22,674,000
Investment, Identifier [Axis]: AuditBoard, Inc., Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (101,000)    
Fair value, ending balance [10],[14]     (101,000)
Investment, Identifier [Axis]: AuditBoard, Inc., Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (41,000)    
Fair value, ending balance [10],[14]     (41,000)
Investment, Identifier [Axis]: Avalara, Inc. , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,021,000    
Investment, Identifier [Axis]: Avalara, Inc., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: Avalara, Inc., Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 60,192,000    
Fair value, ending balance [9],[10]     60,192,000
Investment, Identifier [Axis]: Avaya Holdings Corp., Technology      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,149,000    
Fair value, ending balance 1,973,000   2,149,000
Investment, Identifier [Axis]: Avaya Holdings Corp., Technology 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 528,000    
Fair value, ending balance 671,000   528,000
Investment, Identifier [Axis]: Avaya Holdings Corp., Technology 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 104,000    
Fair value, ending balance 132,000   104,000
Investment, Identifier [Axis]: Aventine Holdings, LLC , Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 16,153,000    
Fair value, ending balance [9],[10]     16,153,000
Investment, Identifier [Axis]: Aventine Holdings, LLC , Media/Entertainment 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 16,386,000    
Investment, Identifier [Axis]: Aventine Holdings, LLC , Media/Entertainment 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 37,531,000    
Fair value, ending balance 41,393,000 [7],[8],[11]   37,531,000 [9],[10]
Investment, Identifier [Axis]: Aventine Holdings, LLC, Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 39,455,000    
Investment, Identifier [Axis]: Aventine Holdings, LLC, Media/Entertainment 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 40,802,000    
Fair value, ending balance [9],[10],[12]     40,802,000
Investment, Identifier [Axis]: Axiom Global, Inc. , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 46,896,000    
Investment, Identifier [Axis]: Axiom Global, Inc., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[12] 45,600,000    
Fair value, ending balance [9],[12]     45,600,000
Investment, Identifier [Axis]: Azurite Intermediate Holdings, Inc. , Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 9,961,000    
Investment, Identifier [Axis]: Azurite Intermediate Holdings, Inc. , Software/Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: Azurite Intermediate Holdings, Inc., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: Azurite Intermediate Holdings, Inc., Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 9,961,000    
Fair value, ending balance [10]     9,961,000
Investment, Identifier [Axis]: Azurite Intermediate Holdings, Inc., Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 22,639,000    
Fair value, ending balance 22,639,000 [8]   22,639,000 [10]
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc. , Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[16] 2,221,000    
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc. , Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[16] 1,165,000    
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc. , Healthcare 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11],[16] 13,758,000    
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc. , Healthcare 6      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 4,985,000    
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[15] 2,641,000    
Fair value, ending balance [10],[15]     2,641,000
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc., Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12],[15] 2,717,000    
Fair value, ending balance [9],[10],[12],[15]     2,717,000
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc., Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[15] 1,380,000    
Fair value, ending balance [9],[10],[15]     1,380,000
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc., Healthcare 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12],[15] 16,302,000    
Fair value, ending balance 2,293,000 [7],[8],[11],[16]   16,302,000 [9],[10],[12],[15]
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc., Healthcare 5      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: Baldwin Insurance Group Holdings, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,526,000    
Fair value, ending balance 3,490,000   3,526,000
Investment, Identifier [Axis]: Bally's Corp., Gaming/Lodging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,492,000    
Fair value, ending balance     3,492,000
Investment, Identifier [Axis]: Battalion CLO, Ltd. 21-17A F, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,023,000    
Fair value, ending balance 865,000   1,023,000
Investment, Identifier [Axis]: Beach Acquisition Bidco, LLC , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 1,457,000    
Investment, Identifier [Axis]: Bella Holding Co., LLC , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 8,089,000    
Investment, Identifier [Axis]: Bella Holding Co., LLC, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 8,149,000    
Fair value, ending balance     8,149,000
Investment, Identifier [Axis]: Belron Finance 2019, LLC , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,833,000    
Fair value, ending balance 5,777,000   5,833,000
Investment, Identifier [Axis]: Berlin Packaging, LLC , Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,048,000    
Fair value, ending balance     3,048,000
Investment, Identifier [Axis]: Big Apple Advisory, LLC , Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (208,000)    
Investment, Identifier [Axis]: Big Apple Advisory, LLC , Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (58,000)    
Investment, Identifier [Axis]: Big Apple Advisory, LLC , Business Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 46,973,000    
Investment, Identifier [Axis]: Big Apple Advisory, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 47,055,000    
Fair value, ending balance [9],[10],[12]     47,055,000
Investment, Identifier [Axis]: Big Apple Advisory, LLC, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (225,000)    
Fair value, ending balance [10],[14]     (225,000)
Investment, Identifier [Axis]: Big Apple Advisory, LLC, Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (63,000)    
Fair value, ending balance [10],[14]     (63,000)
Investment, Identifier [Axis]: Bingo Group Buyer, Inc. , Utilities 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 5,437,000    
Investment, Identifier [Axis]: Bingo Group Buyer, Inc., Utilities 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 20,000    
Investment, Identifier [Axis]: Bingo Group Buyer, Inc., Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 5,401,000    
Fair value, ending balance [9],[10]     5,401,000
Investment, Identifier [Axis]: Bingo Group Buyer, Inc., Utilities 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (20,000)    
Fair value, ending balance 229,000 [8],[13]   (20,000) [10],[14]
Investment, Identifier [Axis]: Bingo Group Buyer, Inc., Utilities 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 12,000    
Fair value, ending balance [10],[14]     12,000
Investment, Identifier [Axis]: Black Mountain Sand, LLC, Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18] 1,305,000    
Fair value, ending balance 1,305,000 [8],[19],[20]   1,305,000 [10],[17],[18]
Investment, Identifier [Axis]: Blackhawk Network Holdings, Inc. , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,030,000    
Fair value, ending balance 4,973,000   5,030,000
Investment, Identifier [Axis]: Blackstone CQP Holdco, LP , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 12,367,000    
Fair value, ending balance 4,938,000   12,367,000
Investment, Identifier [Axis]: Broadstreet Partners, Inc. , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,855,000    
Fair value, ending balance     1,855,000
Investment, Identifier [Axis]: Brown Group Holding, LLC , Other      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,999,000    
Fair value, ending balance     2,999,000
Investment, Identifier [Axis]: Brown Group Holding, LLC, Other      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,978,000    
Investment, Identifier [Axis]: CCI Buyer, Inc. , Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,420,000    
Fair value, ending balance     7,420,000
Investment, Identifier [Axis]: CCI Buyer, Inc. , Telecom 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (30,000)    
Investment, Identifier [Axis]: CCI Buyer, Inc., Telecom 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 51,747,000    
Investment, Identifier [Axis]: CD&R Hydra Buyer, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,265,000    
Fair value, ending balance     6,265,000
Investment, Identifier [Axis]: CD&R Hydra Buyer, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,114,000    
Investment, Identifier [Axis]: CNT Holdings I Corp. , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,388,000    
Fair value, ending balance     3,388,000
Investment, Identifier [Axis]: CNT Holdings I Corp. , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 3,368,000    
Investment, Identifier [Axis]: CPV Shore Holdings, LLC , Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,978,000    
Fair value, ending balance     1,978,000
Investment, Identifier [Axis]: CRS-SPV, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21],[22] 2,008,000    
Investment, Identifier [Axis]: CRS-SPV, Inc., Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0   0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,704,000 0 0
Gross additions 0   1,559,000
Gross reductions 0   2,000
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) 304,000   143,000
Fair value, ending balance 2,008,000   1,704,000
Investment, Identifier [Axis]: CRS-SPV, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23],[24] 1,704,000    
Fair value, ending balance [10],[18],[23],[24]     1,704,000
Investment, Identifier [Axis]: CRS-SPV, Inc., Senior Secured First Lien Debt      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     45,000
Gross reductions     (45,000)
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: Cablevision Lightpath, LLC , Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,815,000    
Fair value, ending balance     2,815,000
Investment, Identifier [Axis]: Cablevision Lightpath, LLC, Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,894,000    
Investment, Identifier [Axis]: Caesars Entertainment, Inc. , Gaming/Lodging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 8,742,000    
Fair value, ending balance 4,966,000   8,742,000
Investment, Identifier [Axis]: Calpine Construction Finance Co., LP , Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,486,000    
Fair value, ending balance     2,486,000
Investment, Identifier [Axis]: Camelot Return Merger Sub, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 1,270,000    
Investment, Identifier [Axis]: Capstone Acquisition Holdings, Inc. , Transportation 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: Capstone Acquisition Holdings, Inc. , Transportation 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 20,654,000    
Investment, Identifier [Axis]: Capstone Logistics , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: Capstone Logistics, Transportation 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 20,758,000    
Fair value, ending balance [9],[10]     20,758,000
Investment, Identifier [Axis]: Carlyle GMS CLO, 16-3A FRR, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,823,000    
Fair value, ending balance 1,823,000   1,823,000
Investment, Identifier [Axis]: Carr, Riggs & Ingram Capital, LLC , Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 1,202,000    
Investment, Identifier [Axis]: Carr, Riggs & Ingram Capital, LLC , Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (25,000)    
Investment, Identifier [Axis]: Carr, Riggs & Ingram Capital, LLC , Business Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 11,572,000    
Investment, Identifier [Axis]: Carr, Riggs & Ingram Capital, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 11,593,000    
Fair value, ending balance [9],[10],[12]     11,593,000
Investment, Identifier [Axis]: Carr, Riggs & Ingram Capital, LLC, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (58,000)    
Fair value, ending balance [10],[14]     (58,000)
Investment, Identifier [Axis]: Carr, Riggs & Ingram Capital, LLC, Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 313,000    
Fair value, ending balance [10],[14]     313,000
Investment, Identifier [Axis]: Center Phase Energy, LLC , Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 10,305,000    
Investment, Identifier [Axis]: Center Phase Energy, LLC, Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 10,305,000    
Fair value, ending balance 2,386,000 [8],[20],[25]   10,305,000 [9],[10]
Investment, Identifier [Axis]: Center Phase Energy, LLC, Utilities 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[26] 2,386,000    
Fair value, ending balance [10],[18],[26]     2,386,000
Investment, Identifier [Axis]: Charter Communications Operating, LLC, Cable      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 352,000    
Fair value, ending balance     352,000
Investment, Identifier [Axis]: Cirque Du Soleil Holding USA Newco, Inc. , Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,284,000    
Fair value, ending balance 7,161,000   7,284,000
Investment, Identifier [Axis]: Cirque Du Soleil Holding USA Newco, Inc. , Media/Entertainment 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [20],[21],[27] 6,045,000    
Investment, Identifier [Axis]: Cirque Du Soleil Holding USA Newco, Inc. , Media/Entertainment 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [20],[21],[27] 2,404,000    
Investment, Identifier [Axis]: Cirque Du Soleil Holding USA Newco, Inc., Media/Entertainment 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [18],[23],[28] 7,016,000    
Fair value, ending balance [18],[23],[28]     7,016,000
Investment, Identifier [Axis]: Cirque Du Soleil Holding USA Newco, Inc., Media/Entertainment 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [18],[23],[28] 3,132,000    
Fair value, ending balance [18],[23],[28]     3,132,000
Investment, Identifier [Axis]: Citadel Securities, LP , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,465,000    
Fair value, ending balance 4,449,000   4,465,000
Investment, Identifier [Axis]: Clarios Global, LP , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 10,006,000    
Investment, Identifier [Axis]: Cliffwater, LLC , Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (29,000)    
Investment, Identifier [Axis]: Cliffwater, LLC , Financials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 30,012,000    
Investment, Identifier [Axis]: Clover Holding 2, LLC , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,303,000    
Fair value, ending balance 5,252,000   5,303,000
Investment, Identifier [Axis]: Clover Technologies Group, LLC Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21] 0    
Investment, Identifier [Axis]: Clover Technologies Group, LLC , Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21] 0    
Investment, Identifier [Axis]: Clover Technologies Group, LLC, Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 628,000    
Fair value, ending balance [10],[18],[23]     628,000
Investment, Identifier [Axis]: Clover Technologies Group, LLC, Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 0    
Fair value, ending balance [10],[18],[23]     0
Investment, Identifier [Axis]: Cold Spring Brewing, Co. , Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 22,655,000    
Investment, Identifier [Axis]: Cold Spring Brewing, Co., Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 23,913,000    
Fair value, ending balance [9],[10],[12]     23,913,000
Investment, Identifier [Axis]: CommerceHub, Inc. , Technology      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,684,000    
Fair value, ending balance     4,684,000
Investment, Identifier [Axis]: CommerceHub, Inc. , Technology      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,877,000    
Investment, Identifier [Axis]: CommerceHub, Inc., Technology      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 7,980,000    
Fair value, ending balance 9,013,000   7,980,000 [10]
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC , Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 1,188,000    
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC , Business Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 24,480,000    
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC , Business Services 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 8,627,000    
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 1,188,000    
Fair value, ending balance [10],[14]     1,188,000
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 24,930,000    
Fair value, ending balance [9],[10]     24,930,000
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC, Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 24,603,000    
Fair value, ending balance 24,801,000 [7],[8]   24,603,000 [9],[10]
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC, Business Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 8,672,000    
Fair value, ending balance [9],[10],[12]     8,672,000
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC, Business Services 5      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 2,432,000    
Investment, Identifier [Axis]: Compass Power Generation, LLC , Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,290,000    
Fair value, ending balance 6,954,000   7,290,000
Investment, Identifier [Axis]: Connect Finco SARL , Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,148,000    
Fair value, ending balance     2,148,000
Investment, Identifier [Axis]: Connect Finco SARL , Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,168,000    
Investment, Identifier [Axis]: Connectwise, LLC , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 12,826,000    
Fair value, ending balance 12,746,000   12,826,000
Investment, Identifier [Axis]: Conservice Midco, LLC , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,516,000    
Fair value, ending balance 7,435,000   7,516,000
Investment, Identifier [Axis]: Consolidated Precision Products Corp., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17] 24,956,000    
Fair value, ending balance 23,636,000 [8],[19]   24,956,000 [10],[17]
Investment, Identifier [Axis]: Corelogic, Inc. , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,867,000    
Fair value, ending balance     6,867,000
Investment, Identifier [Axis]: Corelogic, Inc. , Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,848,000    
Investment, Identifier [Axis]: Corelogic, Inc., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9] 8,994,000    
Fair value, ending balance 8,984,000 [7]   8,994,000 [9]
Investment, Identifier [Axis]: Corelogic, Inc., Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 1,908,000    
Investment, Identifier [Axis]: Corfin Industries, LLC , Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 1,550,000    
Investment, Identifier [Axis]: Corfin Industries, LLC , Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 9,436,000    
Investment, Identifier [Axis]: Corfin Industries, LLC , Industrials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 19,585,000    
Investment, Identifier [Axis]: Corfin Industries, LLC , Industrials 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 15,851,000    
Investment, Identifier [Axis]: Corfin Industries, LLC, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 16,017,000    
Fair value, ending balance [9],[10],[12]     16,017,000
Investment, Identifier [Axis]: Corfin Industries, LLC, Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 1,566,000    
Fair value, ending balance [10]     1,566,000
Investment, Identifier [Axis]: Corfin Industries, LLC, Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 9,532,000    
Fair value, ending balance [10]     9,532,000
Investment, Identifier [Axis]: Cornerstone Building Brands, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,322,000    
Fair value, ending balance 2,947,000   1,322,000
Investment, Identifier [Axis]: Cornerstone Building Brands, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,239,000    
Fair value, ending balance     3,239,000
Investment, Identifier [Axis]: Cornerstone Chemical, Co. , Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21] 3,107,000    
Investment, Identifier [Axis]: Cornerstone Chemical, Co., Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 10,217,000    
Fair value, ending balance [10],[18],[23]     10,217,000
Investment, Identifier [Axis]: Cornerstone Chemical, Co., Chemicals 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18] 884,000    
Fair value, ending balance [10],[18]     884,000
Investment, Identifier [Axis]: Coronis Health I, LLC , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21],[22] 4,900,000    
Investment, Identifier [Axis]: Coronis Health I, LLC 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13],[22] 532,000    
Investment, Identifier [Axis]: Coronis Health I, LLC 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[22] 3,990,000    
Investment, Identifier [Axis]: Coronis Health I, LLC, Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0    
Gross additions 4,900,000    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) 0    
Fair value, ending balance 4,900,000   0
Investment, Identifier [Axis]: Coronis Health I, LLC, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[22] 2,682,000    
Investment, Identifier [Axis]: Coronis Health I, LLC, Senior Secured First Lien Debt 1      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 9,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0    
Gross additions 532,000    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) 0    
Fair value, ending balance 532,000   0
Investment, Identifier [Axis]: Coronis Health I, LLC, Senior Secured First Lien Debt 2      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 69,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0    
Gross additions 3,990,000    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) 0    
Fair value, ending balance 3,990,000   0
Investment, Identifier [Axis]: Coronis Health I, LLC, Senior Secured Second Lien Debt      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 22,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0    
Gross additions 2,682,000    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) 0    
Fair value, ending balance 2,682,000   0
Investment, Identifier [Axis]: Coronis Health, LLC , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[15] 801,000    
Fair value, ending balance [10],[15]     801,000
Investment, Identifier [Axis]: Coronis Health, LLC, Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[15] 9,908,000    
Fair value, ending balance [9],[10],[15]     9,908,000
Investment, Identifier [Axis]: Cotiviti, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,969,000    
Fair value, ending balance     9,969,000
Investment, Identifier [Axis]: Cotiviti, Inc. , Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,722,000    
Investment, Identifier [Axis]: Cotiviti, Inc. , Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 9,820,000    
Investment, Identifier [Axis]: Covenant Credit Partners CLO, Ltd. 17 1A E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,445,000    
Fair value, ending balance     2,445,000
Investment, Identifier [Axis]: Crisis Prevention Institute, Inc. , Education      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,336,000    
Fair value, ending balance     2,336,000
Investment, Identifier [Axis]: Crisis Prevention Institute, Inc., Education      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,319,000    
Investment, Identifier [Axis]: Crown Finance US, Inc. , Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,994,000    
Fair value, ending balance 4,969,000   4,994,000
Investment, Identifier [Axis]: Danish CRJ, Ltd., Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0   0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions 0   0
Gross reductions 0   0
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) 0   0
Fair value, ending balance 0   0
Investment, Identifier [Axis]: Danish CRJ, Ltd., Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23],[28],[29],[30] 0    
Fair value, ending balance 0 [8],[20],[21],[27],[31],[32]   0 [10],[18],[23],[28],[29],[30]
Investment, Identifier [Axis]: Demakes Borrower, LLC , Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 17,667,000    
Investment, Identifier [Axis]: Demakes Borrower, LLC, Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: Demakes Borrower, LLC, Food & Beverage 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 17,756,000    
Fair value, ending balance [9],[10]     17,756,000
Investment, Identifier [Axis]: Directv Financing, LLC , Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,796,000    
Fair value, ending balance 561,000   1,796,000
Investment, Identifier [Axis]: Division Holding Corp. , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,892,000    
Fair value, ending balance     7,892,000
Investment, Identifier [Axis]: Division Holding Corp., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9] 3,413,000    
Fair value, ending balance [9]     3,413,000
Investment, Identifier [Axis]: Dynagrid Holdings, LLC, Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 3,633,000    
Fair value, ending balance [9],[10]     3,633,000
Investment, Identifier [Axis]: Dynagrid Holdings, LLC, Utilities 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 8,873,000    
Fair value, ending balance [9],[10],[12]     8,873,000
Investment, Identifier [Axis]: Dynagrid Holdings, LLC, Utilities 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 3,094,000    
Fair value, ending balance [9],[10],[12]     3,094,000
Investment, Identifier [Axis]: Dynagrid Holdings, LLC, Utilities 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[12] 13,230,000    
Fair value, ending balance [10],[12]     13,230,000
Investment, Identifier [Axis]: Dyno Acquiror, Inc Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 21,000    
Fair value, ending balance [10],[18],[23]     21,000
Investment, Identifier [Axis]: Dyno Acquiror, Inc. , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21] 21,000    
Investment, Identifier [Axis]: EIG Management Co., LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,127,000    
Fair value, ending balance 3,737,000   4,127,000
Investment, Identifier [Axis]: Eaton Vance CDO, Ltd. 15-1A FR, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,495,000    
Fair value, ending balance 1,368,000   1,495,000
Investment, Identifier [Axis]: Edelman Financial Center, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,756,000    
Investment, Identifier [Axis]: Edelman Financial Center, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,783,000    
Fair value, ending balance     4,783,000
Investment, Identifier [Axis]: Edelman Financial Center, LLC), Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9] 9,565,000    
Fair value, ending balance [9]     9,565,000
Investment, Identifier [Axis]: Edelman Financial Center, LLC, Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7] 9,512,000    
Investment, Identifier [Axis]: Edgewater Generation, LLC , Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,403,000    
Fair value, ending balance 7,271,000   7,403,000
Investment, Identifier [Axis]: Einstein Parent, Inc., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (43,000)    
Investment, Identifier [Axis]: Einstein Parent, Inc., Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 21,905,000    
Investment, Identifier [Axis]: Electric Power Engineers, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 27,630,000    
Fair value, ending balance 27,649,000 [7],[8],[11]   27,630,000 [9],[10],[12]
Investment, Identifier [Axis]: Electric Power Engineers, LLC, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (133,000)    
Fair value, ending balance (124,000) [8],[13]   (133,000) [10],[14]
Investment, Identifier [Axis]: Electric Power Engineers, LLC, Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (53,000)    
Fair value, ending balance (49,000) [8],[13]   (53,000) [10],[14]
Investment, Identifier [Axis]: Electro-Methods, LP, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (118,000)    
Investment, Identifier [Axis]: Electro-Methods, LP, Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 34,094,000    
Investment, Identifier [Axis]: Electron Bidco, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,507,000    
Fair value, ending balance     2,507,000
Investment, Identifier [Axis]: Elevation CLO, Ltd. 13-1A D2, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,668,000    
Fair value, ending balance     1,668,000
Investment, Identifier [Axis]: Eliassen Group, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 1,358,000    
Fair value, ending balance 1,351,000 [7],[8]   1,358,000 [9],[10]
Investment, Identifier [Axis]: Eliassen Group, LLC, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 16,976,000    
Fair value, ending balance 16,889,000 [7],[8],[11]   16,976,000 [9],[10],[12]
Investment, Identifier [Axis]: Emerald Borrower, LP , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,300,000    
Investment, Identifier [Axis]: Emerald Borrower, LP, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,332,000    
Fair value, ending balance     5,332,000
Investment, Identifier [Axis]: Ensemble RCM, LLC , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,328,000    
Fair value, ending balance 13,427,000   9,328,000
Investment, Identifier [Axis]: Entain, PLC , Gaming/Lodging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,492,000    
Fair value, ending balance 3,478,000   3,492,000
Investment, Identifier [Axis]: Epicor Software Corp. , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,033,000    
Fair value, ending balance 6,113,000   4,033,000
Investment, Identifier [Axis]: Examworks Bidco, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 1,097,000    
Investment, Identifier [Axis]: FBLC Senior Loan Fund, LLC , Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[32],[33] 304,934,000    
Investment, Identifier [Axis]: FBLC Senior Loan Fund, LLC , Joint Venture      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 15,064,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 404,934,000    
Gross additions 0    
Gross reductions (100,000,000)    
Realized Gain/(Loss) (164,000)    
Change in Unrealized Gain (Loss) 164,000    
Fair value, ending balance 304,934,000   404,934,000
Investment, Identifier [Axis]: FBLC Senior Loan Fund, LLC, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[28],[30],[34] 404,934,000    
Fair value, ending balance [10],[18],[28],[30],[34]     404,934,000
Investment, Identifier [Axis]: FBLC Senior Loan Fund, LLC, Joint Venture      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     31,969,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 404,934,000 0 0
Gross additions     404,934,000
Gross reductions     501,000
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     (501,000)
Fair value, ending balance     404,934,000
Investment, Identifier [Axis]: FGT Purchaser, LLC , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 26,629,000    
Investment, Identifier [Axis]: FGT Purchaser, LLC, Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 2,697,000    
Fair value, ending balance [10]     2,697,000
Investment, Identifier [Axis]: FGT Purchaser, LLC, Consumer 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 26,365,000    
Fair value, ending balance [9],[10]     26,365,000
Investment, Identifier [Axis]: FNZ Group Entities, Ltd. , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,084,000    
Investment, Identifier [Axis]: FNZ Group Entities, Ltd., Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,869,000    
Fair value, ending balance     4,869,000
Investment, Identifier [Axis]: Faraday Buyer, LLC , Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (92,000)    
Fair value, ending balance [10],[14]     (92,000)
Investment, Identifier [Axis]: Faraday Buyer, LLC, Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (423,000)    
Investment, Identifier [Axis]: Faraday Buyer, LLC, Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (92,000)    
Investment, Identifier [Axis]: Faraday Buyer, LLC, Utilities 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 40,542,000    
Fair value, ending balance 40,336,000 [7],[8]   40,542,000 [9],[10]
Investment, Identifier [Axis]: Faraday Buyer, LLC, Utilities 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 8,589,000    
Fair value, ending balance 8,545,000 [7],[8]   8,589,000 [9],[10]
Investment, Identifier [Axis]: Fiesta Purchaser, Inc. , Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,480,000    
Investment, Identifier [Axis]: Fiesta Purchaser, Inc., Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,487,000    
Fair value, ending balance     2,487,000
Investment, Identifier [Axis]: FinThrive Software Intermediate Holdings, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,985,000    
Investment, Identifier [Axis]: FinThrive Software Intermediate Holdings, Inc. , Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,975,000    
Fair value, ending balance     1,975,000
Investment, Identifier [Axis]: FinThrive Software Intermediate Holdings, Inc. , Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,960,000    
Fair value, ending balance     2,960,000
Investment, Identifier [Axis]: First Advantage Holdings, LLC , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,456,000    
Investment, Identifier [Axis]: First Advantage Holdings, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,544,000    
Fair value, ending balance     4,544,000
Investment, Identifier [Axis]: First Brands Group, LLC , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,563,000    
Fair value, ending balance 5,572,000   5,563,000
Investment, Identifier [Axis]: First Eagle Greenway Fund II, LLC , Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [20],[21],[22],[27] 255,000    
Investment, Identifier [Axis]: First Eagle Greenway Fund II, LLC, Diversified Investment Vehicles 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [18],[23],[24],[28] 255,000    
Fair value, ending balance [18],[23],[24],[28]     255,000
Investment, Identifier [Axis]: First Eagle Greenway Fund II, LLC, Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0   0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 255,000 0 0
Gross additions 0   374,000
Gross reductions 0   1,000
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) 0   (120,000)
Fair value, ending balance 255,000   255,000
Investment, Identifier [Axis]: Fitness International, LLC , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,975,000    
Fair value, ending balance 9,885,000   9,975,000
Investment, Identifier [Axis]: FloWorks International, LLC, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (49,000)    
Fair value, ending balance (45,000) [8],[13]   (49,000) [10],[14]
Investment, Identifier [Axis]: FloWorks International, LLC, Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 39,272,000    
Fair value, ending balance 39,205,000 [7],[8],[11]   39,272,000 [9],[10],[12]
Investment, Identifier [Axis]: Florida Food Products, LLC , Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 10,603,000    
Fair value, ending balance [9],[10]     10,603,000
Investment, Identifier [Axis]: Florida Food Products, LLC, Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 9,638,000    
Investment, Identifier [Axis]: Focus Financial Partners, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,948,000    
Investment, Identifier [Axis]: Focus Financial Partners, LLC , Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,000    
Fair value, ending balance     7,000
Investment, Identifier [Axis]: Focus Financial Partners, LLC , Financials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 8,195,000    
Fair value, ending balance     8,195,000
Investment, Identifier [Axis]: Foley Products Co., LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,209,000    
Investment, Identifier [Axis]: Foley Products Co., LLC, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,407,000    
Fair value, ending balance     2,407,000
Investment, Identifier [Axis]: Foresight Energy Operating, LLC , Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 656,000    
Fair value, ending balance 652,000   656,000
Investment, Identifier [Axis]: Foresight Energy Operating, LLC, Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 1,051,000    
Fair value, ending balance 1,044,000 [8]   1,051,000 [10]
Investment, Identifier [Axis]: Foresight Energy Operating, LLC, Energy 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23] 779,000    
Fair value, ending balance 876,000 [8],[19],[20],[21]   779,000 [10],[17],[18],[23]
Investment, Identifier [Axis]: Fortress Credit BSL, Ltd. 22-1A E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 993,000    
Fair value, ending balance     993,000
Investment, Identifier [Axis]: Foundation Building Materials, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 12,108,000    
Fair value, ending balance 7,602,000   12,108,000
Investment, Identifier [Axis]: Freeport LNG Investments, LLLP , Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 5,419,000    
Investment, Identifier [Axis]: Freeport LNG Investments, LLLP , Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,826,000    
Fair value, ending balance     5,826,000
Investment, Identifier [Axis]: GFL Environmental, Inc., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,883,000    
Fair value, ending balance     1,883,000
Investment, Identifier [Axis]: GIP Pilot Acquisition Partners, LP, Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,248,000    
Fair value, ending balance     1,248,000
Investment, Identifier [Axis]: GVC Holdings Gibraltar, Ltd. , Gaming/Lodging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,836,000    
Fair value, ending balance     4,836,000
Investment, Identifier [Axis]: GVC Holdings Gibraltar, Ltd., Gaming/Lodging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,801,000    
Investment, Identifier [Axis]: Galaxy US OpCo, Inc. , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,850,000    
Fair value, ending balance 4,394,000   6,850,000
Investment, Identifier [Axis]: Galway Borrower, LLC , Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 1,043,000    
Investment, Identifier [Axis]: Galway Borrower, LLC, Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 38,532,000    
Fair value, ending balance 38,316,000 [7],[8]   38,532,000 [9],[10]
Investment, Identifier [Axis]: Galway Borrower, LLC, Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 278,000    
Fair value, ending balance [10],[14]     278,000
Investment, Identifier [Axis]: Galway Borrower, LLC, Financials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 81,000    
Fair value, ending balance 732,000 [8],[13]   81,000 [10],[14]
Investment, Identifier [Axis]: Genesys Cloud Services Holdings I, LLC, Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,827,000    
Fair value, ending balance     4,827,000
Investment, Identifier [Axis]: Geon Performance Solutions, LLC , Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,568,000    
Fair value, ending balance 4,297,000   4,568,000
Investment, Identifier [Axis]: Geosyntec Consultants, Inc. , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,308,000    
Fair value, ending balance 9,238,000   9,308,000
Investment, Identifier [Axis]: Global Medical Response, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,989,000    
Fair value, ending balance 9,952,000   9,989,000
Investment, Identifier [Axis]: Golden State Foods, LLC , Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,551,000    
Fair value, ending balance 6,475,000   6,551,000
Investment, Identifier [Axis]: Gordian Medical, Inc, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 0    
Fair value, ending balance 0 [8],[20],[21]   0 [10],[18],[23]
Investment, Identifier [Axis]: Gordian Medical, Inc, Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[18],[23] 2,875,000    
Fair value, ending balance [9],[10],[18],[23]     2,875,000
Investment, Identifier [Axis]: Gordian Medical, Inc. , Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[20],[21] 2,944,000    
Investment, Identifier [Axis]: Gordian Medical, Inc., Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,146,000    
Fair value, ending balance 7,316,000   7,146,000
Investment, Identifier [Axis]: Gordian Medical, Inc., Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0    
Fair value, ending balance 0   0
Investment, Identifier [Axis]: Green Energy Partners/Stonewall, LLC, Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9] 14,617,000    
Fair value, ending balance 14,487,000   14,617,000 [9]
Investment, Identifier [Axis]: Green Energy Partners/Stonewall, LLC, Utilities 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,451,000    
Fair value, ending balance 7,385,000   7,451,000
Investment, Identifier [Axis]: Greywolf CLO, Ltd. 20-3RA ER, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 898,000    
Fair value, ending balance 927,000   898,000
Investment, Identifier [Axis]: Ground Penetrating Radar Systems, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 8,251,000    
Fair value, ending balance [9],[10],[12]     8,251,000
Investment, Identifier [Axis]: Ground Penetrating Radar Systems, LLC, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: Ground Penetrating Radar Systems, LLC, Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 131,000    
Fair value, ending balance [10],[14]     131,000
Investment, Identifier [Axis]: Gulfside Supply, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,744,000    
Fair value, ending balance     4,744,000
Investment, Identifier [Axis]: Gulfside Supply, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,665,000    
Investment, Identifier [Axis]: Hamilton Projects Acquiror, LLC , Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,030,000    
Fair value, ending balance     7,030,000
Investment, Identifier [Axis]: Hamilton Projects Acquiror, LLC, Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,839,000    
Investment, Identifier [Axis]: Hayfin Kingsland XI, Ltd. 19-2A ER, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,474,000    
Fair value, ending balance     2,474,000
Investment, Identifier [Axis]: HealthEdge Software, Inc, Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 21,429,000    
Fair value, ending balance [9],[10],[12]     21,429,000
Investment, Identifier [Axis]: HealthEdge Software, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 9,453,000    
Fair value, ending balance [10]     9,453,000
Investment, Identifier [Axis]: HealthEdge Software, Inc., Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (27,000)    
Fair value, ending balance [10],[14]     (27,000)
Investment, Identifier [Axis]: Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21] 0    
Investment, Identifier [Axis]: HelpSystems Holdings, Inc. , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,404,000    
Fair value, ending balance 6,890,000   6,404,000
Investment, Identifier [Axis]: Higginbotham Insurance Agency, Inc., Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 10,046,000    
Fair value, ending balance 10,046,000 [8],[20]   10,046,000 [10],[18],[23]
Investment, Identifier [Axis]: Highbridge Loan Management, Ltd. 11A-17 E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,513,000    
Fair value, ending balance 2,573,000   2,513,000
Investment, Identifier [Axis]: Hometown Food, Co., Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 15,723,000    
Investment, Identifier [Axis]: Hospice Care Buyer, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 2,143,000    
Investment, Identifier [Axis]: Hospice Care Buyer, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 2,154,000    
Fair value, ending balance [10]     2,154,000
Investment, Identifier [Axis]: Hospice Care Buyer, Inc., Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 4,661,000    
Fair value, ending balance 4,638,000 [8]   4,661,000 [10]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc., Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 1,649,000    
Fair value, ending balance 1,609,000 [8],[13]   1,649,000 [10],[14]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc., Healthcare 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 3,563,000    
Fair value, ending balance 3,546,000 [7],[8]   3,563,000 [9],[10]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc., Healthcare 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 25,076,000    
Fair value, ending balance 24,952,000 [7],[8]   25,076,000 [9],[10]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc., Healthcare 5      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 8,484,000    
Fair value, ending balance 8,443,000 [7],[8]   8,484,000 [9],[10]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc., Healthcare 6      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 6,509,000    
Fair value, ending balance 6,476,000 [7],[8]   6,509,000 [9],[10]
Investment, Identifier [Axis]: Hudson River Trading, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,296,000    
Fair value, ending balance     5,296,000
Investment, Identifier [Axis]: Hudson River Trading, LLC , Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,494,000    
Investment, Identifier [Axis]: Hudson River Trading, LLC , Financials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 5,267,000    
Investment, Identifier [Axis]: Hunter Douglas, Inc. , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,957,000    
Fair value, ending balance 4,486,000   4,957,000
Investment, Identifier [Axis]: ICP Industrial, Inc. , Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,471,000    
Fair value, ending balance     4,471,000
Investment, Identifier [Axis]: ICR Operations, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 40,839,000    
Investment, Identifier [Axis]: ICR Operations, LLC, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 41,292,000    
Fair value, ending balance 2,219,000 [8]   41,292,000 [10]
Investment, Identifier [Axis]: ICR Operations, LLC, Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 2,243,000    
Fair value, ending balance 2,780,000 [8],[13]   2,243,000 [10]
Investment, Identifier [Axis]: ICR Operations, LLC, Business Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 6,101,000    
Fair value, ending balance [10],[14]     6,101,000
Investment, Identifier [Axis]: ICR Operations, LLC, Business Services 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 1,597,000    
Fair value, ending balance [10],[14]     1,597,000
Investment, Identifier [Axis]: IDERA, Inc. , Technology      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,656,000    
Fair value, ending balance     6,656,000
Investment, Identifier [Axis]: IDERA, Inc. , Technology 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,651,000    
Investment, Identifier [Axis]: IDERA, Inc. , Technology 1.1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 933,000    
Investment, Identifier [Axis]: IDERA, Inc., Technology      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 997,000    
Fair value, ending balance     997,000
Investment, Identifier [Axis]: IG Investments Holdings, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: IG Investments Holdings, LLC, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 26,263,000    
Fair value, ending balance [9],[10]     26,263,000
Investment, Identifier [Axis]: IQN Holding Corp., Software/Service 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 1,115,000    
Investment, Identifier [Axis]: IQN Holding Corp., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 595,000    
Fair value, ending balance [10],[14]     595,000
Investment, Identifier [Axis]: IQN Holding Corp., Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 17,184,000    
Fair value, ending balance 5,699,000 [8]   17,184,000 [9],[10],[12]
Investment, Identifier [Axis]: IQN Holding Corp., Software/Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 17,096,000    
Investment, Identifier [Axis]: IXS Holdings, Inc. , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,166,000    
Fair value, ending balance 7,189,000   7,166,000
Investment, Identifier [Axis]: Icon Parent, Inc. , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,014,000    
Fair value, ending balance     5,014,000
Investment, Identifier [Axis]: Icon Parent, Inc. , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 5,038,000    
Investment, Identifier [Axis]: Icon Parent, Inc. , Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,992,000    
Investment, Identifier [Axis]: Icon Parent, Inc., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,069,000    
Fair value, ending balance     5,069,000
Investment, Identifier [Axis]: Ideal Tridon Holdings, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 7,000    
Fair value, ending balance (78,000) [8],[13]   7,000 [10],[14]
Investment, Identifier [Axis]: Ideal Tridon Holdings, Inc., Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 29,938,000    
Fair value, ending balance (65,000) [8],[13]   29,938,000 [9],[10],[12]
Investment, Identifier [Axis]: Ideal Tridon Holdings, Inc., Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 41,951,000    
Investment, Identifier [Axis]: Ideal Tridon Holdings, Inc., Industrials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: Ideal Tridon Holdings, Inc., Industrials 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 26,132,000    
Investment, Identifier [Axis]: Indigo Buyer, Inc. , Paper & Packaging 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: Indigo Buyer, Inc. , Paper & Packaging 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 11,258,000    
Fair value, ending balance [9],[10]     11,258,000
Investment, Identifier [Axis]: Indigo Buyer, Inc., Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 7,861,000    
Fair value, ending balance 912,000 [8],[13]   7,861,000 [10]
Investment, Identifier [Axis]: Indigo Buyer, Inc., Paper & Packaging 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (114,000)    
Fair value, ending balance [10],[14]     (114,000)
Investment, Identifier [Axis]: Indigo Buyer, Inc., Paper & Packaging 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance 61,186,000 [7],[8]   0 [10],[14]
Investment, Identifier [Axis]: Indigo Buyer, Inc., Paper & Packaging 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 12,661,000    
Fair value, ending balance [9],[10]     12,661,000
Investment, Identifier [Axis]: Indigo Buyer, Inc., Paper & Packaging 5      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 29,600,000    
Fair value, ending balance [9],[10]     29,600,000
Investment, Identifier [Axis]: InhabitIQ, Inc, Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (34,000)    
Investment, Identifier [Axis]: InhabitIQ, Inc. , Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (21,000)    
Investment, Identifier [Axis]: InhabitIQ, Inc.,Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 26,017,000    
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13],[22] (59,000)    
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc, Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[22] 240,000    
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc, Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[22] 1,250,000    
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc, Industrials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (78,000)    
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc, Industrials 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 186,000    
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc, Industrials 5      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 32,277,000    
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc, Industrials 6      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[19],[20],[21],[22] 0    
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[15],[24] 446,000    
Fair value, ending balance [10],[15],[24]     446,000
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Equity/Other Investments 1      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0   0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions 0   0
Gross reductions 0   0
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) 0   0
Fair value, ending balance 0   0
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Equity/Other Investments 2      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0   0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions 0   0
Gross reductions 0   0
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) 0   0
Fair value, ending balance 0   0
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14],[24] 210,000    
Fair value, ending balance 0 [8],[16],[22]   210,000 [10],[14],[24]
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[24] 1,393,000    
Fair value, ending balance [10],[24]     1,393,000
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Industrials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23],[24] 0    
Fair value, ending balance [10],[17],[18],[23],[24]     0
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Industrials 6      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23],[24] 0    
Fair value, ending balance [10],[17],[18],[23],[24]     0
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Industrials 7      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[19],[20],[21],[22] 0    
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Senior Secured First Lien Debt      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 9,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0    
Gross additions 240,000    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) 0    
Fair value, ending balance 240,000   0
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Senior Secured First Lien Debt 1      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 52,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,393,000    
Gross additions 0    
Gross reductions (7,000)    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) (136,000)    
Fair value, ending balance 1,250,000   1,393,000
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Senior Secured First Lien Debt 2      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 16,000   16,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 210,000 0 0
Gross additions 60,000   345,000
Gross reductions (270,000)   (135,000)
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) (59,000)   0
Fair value, ending balance (59,000)   210,000
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Senior Secured First Lien Debt 3      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     99,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,393,000 0 0
Gross additions     1,406,000
Gross reductions     (12,000)
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     (1,000)
Fair value, ending balance     1,393,000
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Senior Secured Second Lien Debt      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 1,000   260,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 446,000 0 0
Gross additions 0   1,074,000
Gross reductions 0   1,000
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) (446,000)   (629,000)
Fair value, ending balance 0   446,000
Investment, Identifier [Axis]: Integrated Global Services, Inc., Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 1,825,000    
Fair value, ending balance [10]     1,825,000
Investment, Identifier [Axis]: Integrated Global Services, Inc., Industrials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: Integrated Global Services, Inc., Industrials 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[12] 13,510,000    
Fair value, ending balance [10],[12]     13,510,000
Investment, Identifier [Axis]: Internap Corp., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[18],[23] 0    
Fair value, ending balance 0 [7],[8],[20],[21]   0 [9],[10],[18],[23]
Investment, Identifier [Axis]: International Cruise & Excursion Gallery, Inc, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[12],[18],[23] 0    
Fair value, ending balance 1,358,000 [8],[11]   0 [10],[12],[18],[23]
Investment, Identifier [Axis]: International Cruise & Excursion Gallery, Inc., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[12] 1,439,000    
Fair value, ending balance 0 [8],[11],[20],[21]   1,439,000 [10],[12]
Investment, Identifier [Axis]: J&K Ingredients, LLC, Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 12,344,000    
Fair value, ending balance 12,282,000 [7],[8]   12,344,000 [9],[10]
Investment, Identifier [Axis]: JSG II, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 396,000    
Investment, Identifier [Axis]: Jack Ohio Finance, LLC , Gaming/Lodging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,881,000    
Fair value, ending balance     3,881,000
Investment, Identifier [Axis]: Jamestown CLO, Ltd. 22-18A E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,975,000    
Fair value, ending balance     2,975,000
Investment, Identifier [Axis]: Jane Street Group, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,124,000    
Investment, Identifier [Axis]: Jane Street Group, LLC , Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,544,000    
Fair value, ending balance     6,544,000
Investment, Identifier [Axis]: Jane Street Group, LLC , Financials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,137,000    
Fair value, ending balance     6,137,000
Investment, Identifier [Axis]: Jazz Securities, DAC, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 943,000    
Fair value, ending balance     943,000
Investment, Identifier [Axis]: Johnstone Supply, LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 984,000    
Fair value, ending balance     984,000
Investment, Identifier [Axis]: Jump Financial, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,232,000    
Fair value, ending balance 7,268,000   7,232,000
Investment, Identifier [Axis]: KKR Financial CLO, Ltd. 15 FR, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,768,000    
Fair value, ending balance 1,795,000   1,768,000
Investment, Identifier [Axis]: Kahala Aviation, LLC , Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,308,000    
Gross additions 6,693,000    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) 426,000    
Fair value, ending balance 9,427,000   2,308,000
Investment, Identifier [Axis]: Kahala Aviation, LLC , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21],[32],[35],[36] 9,427,000    
Investment, Identifier [Axis]: Kahala Aviation, LLC, Subordinated Debt      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 1,325,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0    
Gross additions 27,076,000    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) (31,000)    
Fair value, ending balance 27,045,000   0
Investment, Identifier [Axis]: Kahala Aviation, LLC, Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23],[30],[37],[38] 2,308,000    
Fair value, ending balance 27,045,000 [8],[32]   2,308,000 [10],[18],[23],[30],[37],[38]
Investment, Identifier [Axis]: Kahala Ireland OpCo Designated Activity Company, Equity/Other Investments 1      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     0
Gross reductions     0
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: Kahala Ireland OpCo Designated Activity Company, Equity/Other Investments 2      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     538,000
Gross reductions     (538,000)
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: Kahala US OpCo, LLC, Equity/Other Investments 1      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,308,000 0 0
Gross additions     2,739,000
Gross reductions     75,000
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     (506,000)
Fair value, ending balance     2,308,000
Investment, Identifier [Axis]: Kahala US OpCo, LLC, Equity/Other Investments 2      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     0
Gross reductions     0
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: Kahala US OpCo, LLC, Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23],[28],[30],[37] 0    
Fair value, ending balance 0 [8],[20],[21],[27],[32],[35]   0 [10],[18],[23],[28],[30],[37]
Investment, Identifier [Axis]: Kaman Corp. , Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,220,000    
Investment, Identifier [Axis]: Kaman Corp. , Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance (1,000)    
Investment, Identifier [Axis]: Kaseya, Inc. , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 696,000    
Investment, Identifier [Axis]: Kaseya, Inc. , Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 3,804,000    
Investment, Identifier [Axis]: Kissner Milling Co., Ltd., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[18] 4,950,000    
Fair value, ending balance [9],[18]     4,950,000
Investment, Identifier [Axis]: Knowledge Pro Buyer, Inc, Business Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 0    
Investment, Identifier [Axis]: Knowledge Pro Buyer, Inc, Business Services 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 23,277,000    
Investment, Identifier [Axis]: Knowledge Pro Buyer, Inc, Business Services 5      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 34,772,000    
Investment, Identifier [Axis]: Knowledge Pro Buyer, Inc., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 294,000    
Fair value, ending balance 0 [8],[13]   294,000 [10],[14]
Investment, Identifier [Axis]: Knowledge Pro Buyer, Inc., Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[14] 16,445,000    
Fair value, ending balance 0 [8],[13]   16,445,000 [9],[10],[14]
Investment, Identifier [Axis]: Knowledge Pro Buyer, Inc., Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 34,952,000    
Fair value, ending balance 451,000 [7],[8]   34,952,000 [9],[10],[12]
Investment, Identifier [Axis]: Kuehg Corp. , Education      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,122,000    
Fair value, ending balance 3,079,000   3,122,000
Investment, Identifier [Axis]: LABL, Inc. , Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,787,000    
Fair value, ending balance     4,787,000
Investment, Identifier [Axis]: LABL, Inc., Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,435,000    
Investment, Identifier [Axis]: LBM Acquisition, LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,982,000    
Fair value, ending balance     4,982,000
Investment, Identifier [Axis]: LCM, Ltd. Partnership 16A ER2, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,275,000    
Fair value, ending balance 2,117,000   2,275,000
Investment, Identifier [Axis]: LSF12 Donnelly Bidco, LLC, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 18,930,000    
Fair value, ending balance 18,835,000 [7],[8]   18,930,000 [9],[10]
Investment, Identifier [Axis]: Labrie Environmental Group, LLC, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[28] 21,894,000    
Fair value, ending balance 21,780,000 [8],[27]   21,894,000 [10],[28]
Investment, Identifier [Axis]: Lakeland Tours, LLC , Education      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12],[15] 1,414,000    
Fair value, ending balance [9],[10],[12],[15]     1,414,000
Investment, Identifier [Axis]: Lakeland Tours, LLC, Education      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[11],[16] 1,414,000    
Investment, Identifier [Axis]: Lakeland Tours, LLC, Education 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11],[16] 17,000    
Investment, Identifier [Axis]: Lakeshore Learning Materials, LLC , Retail      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,862,000    
Fair value, ending balance     4,862,000
Investment, Identifier [Axis]: Lakeview Health Holdings, Inc, Senior Secured First Lien Debt 1      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     19,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     714,000
Gross reductions     (714,000)
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: Lakeview Health Holdings, Inc, Senior Secured First Lien Debt 2      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     1,112,000
Gross reductions     (1,112,000)
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: Lakeview Health Holdings, Inc, Senior Secured First Lien Debt 3      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     4,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     130,000
Gross reductions     (130,000)
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: Lakeview Health Holdings, Inc. , Senior Secured First Lien Debt      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income (16,000)    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0    
Gross additions 0    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) 0    
Fair value, ending balance 0   0
Investment, Identifier [Axis]: Lakeview Health Holdings, Inc., Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     0
Gross reductions     0
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: Lakeview Health Holdings, Inc., Senior Secured First Lien Debt 2      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     4,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     227,000
Gross reductions     (227,000)
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: Lakeview Health Holdings, Inc., Senior Secured First Lien Debt 3      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     98,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     2,505,000
Gross reductions     (2,503,000)
Realized Gain/(Loss)     (2,000)
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: Lakeview Health Holdings, Inc., Senior Secured First Lien Debt 4      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     618,000
Gross reductions     (649,000)
Realized Gain/(Loss)     31,000
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: LaserShip, Inc. , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,850,000    
Fair value, ending balance 2,224,000   2,850,000
Investment, Identifier [Axis]: LaserShip, Inc. , Transportation 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9] 1,096,000    
Fair value, ending balance [9]     1,096,000
Investment, Identifier [Axis]: LaserShip, Inc., Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 849,000    
Investment, Identifier [Axis]: LaserShip, Inc., Transportation 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 804,000    
Investment, Identifier [Axis]: LaserShip, Inc., Transportation 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9] 978,000    
Fair value, ending balance [9]     978,000
Investment, Identifier [Axis]: Last Dance Intermediate II, LLC, Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 18,867,000    
Investment, Identifier [Axis]: Last Dance Intermediate II, LLC, Telecom 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (187,000)    
Investment, Identifier [Axis]: Last Dance Intermediate II, LLC, Telecom 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (48,000)    
Investment, Identifier [Axis]: Last Dance Intermediate II, LLC, Telecom 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 19,034,000    
Investment, Identifier [Axis]: LifePoint Health, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,830,000    
Fair value, ending balance 4,767,000   3,830,000
Investment, Identifier [Axis]: LifePoint Health, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,861,000    
Fair value, ending balance     4,861,000
Investment, Identifier [Axis]: Lighthouse Intelligence, Ltd, Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13],[27] (172,000)    
Investment, Identifier [Axis]: Lighthouse Intelligence, Ltd, Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [13],[27] (123,000)    
Investment, Identifier [Axis]: Lighthouse Intelligence, Ltd, Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[27] 22,107,000    
Investment, Identifier [Axis]: Lightning Power, LLC , Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,534,000    
Fair value, ending balance     4,534,000
Investment, Identifier [Axis]: Lightstone Holdco, LLC , Utilities 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 16,025,000    
Fair value, ending balance 15,752,000   16,025,000
Investment, Identifier [Axis]: Lightstone Holdco, LLC , Utilities 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 906,000    
Fair value, ending balance 891,000   906,000
Investment, Identifier [Axis]: Liquid Tech Solutions Holdings, LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,933,000    
Fair value, ending balance 9,884,000   9,933,000
Investment, Identifier [Axis]: Luxembourg Investment Co., 428 SARL, Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 51,000    
Fair value, ending balance     51,000
Investment, Identifier [Axis]: MCS Acquisition Corp. , Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21] 747,000    
Investment, Identifier [Axis]: MCS Acquisition Corp. Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21] 325,000    
Investment, Identifier [Axis]: MCS Acquisition Corp., Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 747,000    
Fair value, ending balance [10],[18],[23]     747,000
Investment, Identifier [Axis]: MCS Acquisition Corp., Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 325,000    
Fair value, ending balance [10],[18],[23]     325,000
Investment, Identifier [Axis]: MGTF Holdco, LLC , Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[19],[20],[21],[32] 0    
Investment, Identifier [Axis]: MGTF Holdco, LLC, Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     0
Gross reductions     0
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: MGTF Holdco, LLC, Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23],[30] 0    
Fair value, ending balance [10],[17],[18],[23],[30]     0
Investment, Identifier [Axis]: MGTF Radio Company, LLC, Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[30] 31,672,000    
Fair value, ending balance 19,809,000 [8],[16],[32]   31,672,000 [10],[30]
Investment, Identifier [Axis]: MGTF Radio Company, LLC, Senior Secured First Lien Debt      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 1,511,000   12,882,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 31,672,000 0 0
Gross additions 105,000   45,598,000
Gross reductions 0   (688,000)
Realized Gain/(Loss) 0   6,000
Change in Unrealized Gain (Loss) (11,968,000)   (13,244,000)
Fair value, ending balance 19,809,000   31,672,000
Investment, Identifier [Axis]: MH Sub I, LLC , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,432,000    
Fair value, ending balance 5,998,000   4,432,000
Investment, Identifier [Axis]: MPH Acquisition Holdings, LLC , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 735,000    
Fair value, ending balance     735,000
Investment, Identifier [Axis]: MPH Acquisition Holdings, LLC , Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 92,000    
Investment, Identifier [Axis]: MPH Acquisition Holdings, LLC , Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 691,000    
Investment, Identifier [Axis]: MRI Software, LLC, Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,198,000    
Fair value, ending balance     2,198,000
Investment, Identifier [Axis]: MRI Software, LLC, Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 588,000    
Fair value, ending balance 2,178,000 [8]   588,000 [10],[14]
Investment, Identifier [Axis]: MRI Software, LLC, Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 5,445,000    
Investment, Identifier [Axis]: MYOB US Borrower, LLC , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,201,000    
Fair value, ending balance     5,201,000
Investment, Identifier [Axis]: Madison IAQ, LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,893,000    
Fair value, ending balance     1,893,000
Investment, Identifier [Axis]: Magnite, Inc., Technology      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,031,000    
Fair value, ending balance     5,031,000
Investment, Identifier [Axis]: Mandrake Bidco, Inc, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: Mandrake Bidco, Inc, Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 59,345,000    
Investment, Identifier [Axis]: Mandrake Bidco, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (96,000)    
Fair value, ending balance [10],[14]     (96,000)
Investment, Identifier [Axis]: Mandrake Bidco, Inc. , Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 62,532,000    
Fair value, ending balance [9],[10],[12]     62,532,000
Investment, Identifier [Axis]: Manna Pro Products, LLC ), Consumer 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[12] 1,570,000    
Fair value, ending balance [10],[12]     1,570,000
Investment, Identifier [Axis]: Manna Pro Products, LLC), Consumer 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 2,208,000    
Fair value, ending balance [10],[14]     2,208,000
Investment, Identifier [Axis]: Manna Pro Products, LLC), Consumer 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[12] 5,645,000    
Fair value, ending balance [10],[12]     5,645,000
Investment, Identifier [Axis]: Manna Pro Products, LLC, Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 3,313,000    
Investment, Identifier [Axis]: Manna Pro Products, LLC, Consumer 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 3,293,000    
Fair value, ending balance (430,000) [8],[13]   3,293,000 [10]
Investment, Identifier [Axis]: Manna Pro Products, LLC, Consumer 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[11] 1,579,000    
Investment, Identifier [Axis]: Manna Pro Products, LLC, Consumer 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[11] 5,680,000    
Investment, Identifier [Axis]: Manna Pro Products, LLC, Consumer 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[11] 20,033,000    
Investment, Identifier [Axis]: Manna Pro Products, LLC, Consumer 5      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[12] 19,909,000    
Fair value, ending balance [10],[12]     19,909,000
Investment, Identifier [Axis]: Max US Bidco, Inc. , Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,822,000    
Fair value, ending balance     4,822,000
Investment, Identifier [Axis]: Max US Bidco, Inc., Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,889,000    
Investment, Identifier [Axis]: McDonald Worley, P.C, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[16] 12,848,000    
Investment, Identifier [Axis]: McDonald Worley, P.C., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[15] 12,442,000    
Fair value, ending balance 3,390,000 [8],[20],[21]   12,442,000 [10],[15]
Investment, Identifier [Axis]: McDonald Worley, P.C., Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 3,140,000    
Fair value, ending balance [10],[18],[23]     3,140,000
Investment, Identifier [Axis]: Medalist Partners Corporate Finance CLO, Ltd. 21-1A D, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,964,000    
Fair value, ending balance     2,964,000
Investment, Identifier [Axis]: Medical Depot Holdings, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 4,155,000    
Fair value, ending balance [10]     4,155,000
Investment, Identifier [Axis]: Medical Depot Holdings, Inc., Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 21,727,000    
Fair value, ending balance 4,257,000 [8]   21,727,000 [9],[10],[12]
Investment, Identifier [Axis]: Medical Depot Holdings, Inc., Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 19,626,000    
Investment, Identifier [Axis]: Medical Management Resource Group, LLC, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 1,361,000    
Investment, Identifier [Axis]: Medical Management Resource Group, LLC, Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 9,279,000    
Fair value, ending balance 9,231,000 [7],[8]   9,279,000 [9],[10]
Investment, Identifier [Axis]: Medical Management Resource Group, LLC, Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 1,207,000    
Fair value, ending balance 22,349,000 [7],[8]   1,207,000 [10],[14]
Investment, Identifier [Axis]: Medical Management Resource Group, LLC, Healthcare 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 22,466,000    
Fair value, ending balance [9],[10]     22,466,000
Investment, Identifier [Axis]: Medline Borrower, LP , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,001,000    
Fair value, ending balance     4,001,000
Investment, Identifier [Axis]: Megavolt Borrower, LLC, Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 36,472,000    
Investment, Identifier [Axis]: Mermaid Bidco, Inc. , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 7,481,000    
Investment, Identifier [Axis]: Michael Baker International, LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 3,239,000    
Investment, Identifier [Axis]: Michael Baker International, LLC, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,253,000    
Fair value, ending balance     3,253,000
Investment, Identifier [Axis]: Midwest Can Company, LLC, Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 29,913,000    
Fair value, ending balance 27,902,000 [7],[8],[11]   29,913,000 [9],[10],[12]
Investment, Identifier [Axis]: Miller Environmental Group, Inc, Business Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (35,000)    
Fair value, ending balance [10],[14]     (35,000)
Investment, Identifier [Axis]: Miller Environmental Group, Inc., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 17,464,000    
Fair value, ending balance 17,387,000 [7],[8],[11]   17,464,000 [9],[10],[12]
Investment, Identifier [Axis]: Miller Environmental Group, Inc., Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (70,000)    
Fair value, ending balance (65,000) [8],[13]   (70,000) [10],[14]
Investment, Identifier [Axis]: Miller Environmental Group, Inc., Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (35,000)    
Fair value, ending balance (32,000) [8],[13]   (35,000) [10],[14]
Investment, Identifier [Axis]: Mirra-Primeaccess Holdings, LLC, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 6,754,000    
Fair value, ending balance [10],[14]     6,754,000
Investment, Identifier [Axis]: Mirra-Primeaccess Holdings, LLC, Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 58,479,000    
Fair value, ending balance 7,316,000 [8],[13]   58,479,000 [9],[10]
Investment, Identifier [Axis]: Mirra-Primeaccess Holdings, LLC, Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 61,599,000    
Investment, Identifier [Axis]: Monogram Food Solutions, LLC , Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,099,000    
Investment, Identifier [Axis]: Motor Vehicle Software Corp., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23],[39] 523,000    
Fair value, ending balance 764,000 [8],[20],[21],[40]   523,000 [10],[18],[23],[39]
Investment, Identifier [Axis]: Muth Mirror Systems, LLC , Technology 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[19],[20],[21] 0    
Investment, Identifier [Axis]: Muth Mirror Systems, LLC, Technology      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 1,083,000    
Fair value, ending balance [10]     1,083,000
Investment, Identifier [Axis]: Muth Mirror Systems, LLC, Technology 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 11,836,000    
Fair value, ending balance 829,000 [8],[16]   11,836,000 [9],[10],[12]
Investment, Identifier [Axis]: Muth Mirror Systems, LLC, Technology 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23] 0    
Fair value, ending balance 8,958,000 [8],[16]   0 [10],[17],[18],[23]
Investment, Identifier [Axis]: Muth Mirror Systems, LLC, Technology 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23] 0    
Fair value, ending balance 0 [8],[19],[20],[21]   0 [10],[17],[18],[23]
Investment, Identifier [Axis]: National Mentor Holdings, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 93,000    
Fair value, ending balance     93,000
Investment, Identifier [Axis]: National Mentor Holdings, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,349,000    
Fair value, ending balance     2,349,000
Investment, Identifier [Axis]: Neptune Bidco US, Inc., Publishing      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,888,000    
Fair value, ending balance 1,711,000   1,888,000
Investment, Identifier [Axis]: New Star Metals, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 28,751,000    
Fair value, ending balance [9],[10],[12]     28,751,000
Investment, Identifier [Axis]: NewStar Arlington Senior Loan Program, LLC 14-1A FR, Collateralized Securities      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 398,000   782,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,237,000 0 0
Gross additions 25,000   4,199,000
Gross reductions 0   7,000
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) (25,000)   31,000
Fair value, ending balance 4,237,000   4,237,000
Investment, Identifier [Axis]: NewStar Arlington Senior Loan Program, LLC 14-1A FR, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[24],[28] 4,237,000    
Fair value, ending balance 4,237,000 [8],[20],[22],[27]   4,237,000 [10],[18],[24],[28]
Investment, Identifier [Axis]: NewStar Arlington Senior Loan Program, LLC 14-1A SUB, Collateralized Securities      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income (88,000)   409,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,170,000 0 0
Gross additions 0   5,472,000
Gross reductions 0   (2,309,000)
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) (761,000)   (993,000)
Fair value, ending balance 1,409,000   2,170,000
Investment, Identifier [Axis]: NewStar Arlington Senior Loan Program, LLC 14-1A SUB, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[24],[28],[41] 2,170,000    
Fair value, ending balance 1,409,000 [8],[20],[22],[27],[42]   2,170,000 [10],[18],[24],[28],[41]
Investment, Identifier [Axis]: Newstar Fairfield Fund CLO, Ltd. 2015-1RA F, Collateralized Securities      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 17,000   1,338,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,457,000 0 0
Gross additions 3,000   9,257,000
Gross reductions (2,457,000)   (7,477,000)
Realized Gain/(Loss) 137,000   536,000
Change in Unrealized Gain (Loss) (140,000)   141,000
Fair value, ending balance 0   2,457,000
Investment, Identifier [Axis]: Newstar Fairfield Fund CLO, Ltd. 2015-1RA F, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[24],[28] 2,457,000    
Fair value, ending balance [10],[18],[24],[28]     2,457,000
Investment, Identifier [Axis]: Newstar Fairfield Fund CLO, Ltd. 2015-1RA SUB, Collateralized Securities      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0   0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,208,000 0 0
Gross additions 0   0
Gross reductions 0   0
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) (696,000)   1,208,000
Fair value, ending balance 512,000   1,208,000
Investment, Identifier [Axis]: Newstar Fairfield Fund CLO, Ltd. 2015-1RA SUB, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[24],[28],[41] 1,208,000    
Fair value, ending balance 512,000 [8],[20],[22],[27],[42]   1,208,000 [10],[18],[24],[28],[41]
Investment, Identifier [Axis]: Nexus Buyer, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,173,000    
Fair value, ending balance 5,001,000   7,173,000
Investment, Identifier [Axis]: Northwoods Capital, Ltd. 17-15A ER, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,959,000    
Fair value, ending balance     2,959,000
Investment, Identifier [Axis]: Norvax, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14],[28] 195,000    
Fair value, ending balance 576,000 [8]   195,000 [10],[14],[28]
Investment, Identifier [Axis]: Nouryon Finance B.V. , Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,261,000    
Fair value, ending balance 2,223,000   2,261,000
Investment, Identifier [Axis]: OCP CLO, Ltd. 14-5A DR, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,085,000    
Fair value, ending balance 2,124,000   2,085,000
Investment, Identifier [Axis]: ORG GC Holdings, LLC (2), Equity/Other Investments 3      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0    
Gross additions 0    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) 0    
Fair value, ending balance 0   0
Investment, Identifier [Axis]: ORG GC Holdings, LLC , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[19],[20],[21],[22] 0    
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[24] 4,999,000    
Fair value, ending balance 10,111,000 [8],[22]   4,999,000 [10],[24]
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[24] 10,112,000    
Fair value, ending balance 4,932,000 [8],[22]   10,112,000 [10],[24]
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23],[24] 0    
Fair value, ending balance 0 [8],[19],[22]   0 [10],[17],[18],[23],[24]
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Business Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23],[24] 0    
Fair value, ending balance [10],[17],[18],[23],[24]     0
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Equity/Other Investments 1      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0   0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions 0   0
Gross reductions 0   0
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) 0   0
Fair value, ending balance 0   0
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Equity/Other Investments 2      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0   0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions 0   0
Gross reductions 0   0
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) 0   0
Fair value, ending balance 0   0
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Senior Secured First Lien Debt      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 565,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 10,112,000    
Gross additions 1,000    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) (2,000)    
Fair value, ending balance 10,111,000   10,112,000
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Senior Secured First Lien Debt 1      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     1,145,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 10,112,000 0 0
Gross additions     10,108,000
Gross reductions     17,000
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     (13,000)
Fair value, ending balance     10,112,000
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Senior Secured First Lien Debt 2      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     3,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 0 0
Gross additions     0
Gross reductions     0
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Senior Secured Second Lien Debt      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 579,000   960,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,999,000 0 0
Gross additions 579,000   5,640,000
Gross reductions 0   8,000
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) (646,000)   (649,000)
Fair value, ending balance 4,932,000   4,999,000
Investment, Identifier [Axis]: OZLM, Ltd. 16-15A DR, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,875,000    
Fair value, ending balance 1,904,000   1,875,000
Investment, Identifier [Axis]: Odessa Technologies, Inc., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: Odessa Technologies, Inc., Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 20,446,000    
Fair value, ending balance 467,000 [8],[13]   20,446,000 [9],[10]
Investment, Identifier [Axis]: Odessa Technologies, Inc., Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 20,341,000    
Investment, Identifier [Axis]: Omnia Partners, LLC , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,240,000    
Fair value, ending balance     6,240,000
Investment, Identifier [Axis]: Omnia Partners, LLC , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,192,000    
Investment, Identifier [Axis]: OneDigital Borrower, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,849,000    
Fair value, ending balance     6,849,000
Investment, Identifier [Axis]: Osaic Holdings, Inc. , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,506,000    
Fair value, ending balance 5,472,000   5,506,000
Investment, Identifier [Axis]: Oscar AcquisitionCo, LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,884,000    
Fair value, ending balance 3,146,000   4,884,000
Investment, Identifier [Axis]: PG&E Corp., Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,946,000    
Fair value, ending balance 8,631,000   6,946,000
Investment, Identifier [Axis]: PODS, LLC , Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,944,000    
Fair value, ending balance 9,094,000   6,944,000
Investment, Identifier [Axis]: PRA Health Sciences, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 8,284,000    
Fair value, ending balance 6,442,000   8,284,000
Investment, Identifier [Axis]: Palmer Square CLO, Ltd. 21-4A F, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,383,000    
Fair value, ending balance 1,408,000   1,383,000
Investment, Identifier [Axis]: Peer Holding III B.V. , Retail      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,024,000    
Fair value, ending balance 5,997,000   6,024,000
Investment, Identifier [Axis]: PennantPark Credit Opportunities Fund II, LP , Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [20],[21],[22],[27] 568,000    
Investment, Identifier [Axis]: PennantPark Credit Opportunities Fund II, LP, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [18],[23],[24],[28] 603,000    
Fair value, ending balance [18],[23],[24],[28]     603,000
Investment, Identifier [Axis]: PennantPark Credit Opportunities Fund II, LP, Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0   0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 603,000 0 0
Gross additions 0   960,000
Gross reductions 0   2,000
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) (35,000)   (359,000)
Fair value, ending balance 568,000   603,000
Investment, Identifier [Axis]: Peraton Corp. , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,297,000    
Investment, Identifier [Axis]: Peraton Corp. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,557,000    
Fair value, ending balance     4,557,000
Investment, Identifier [Axis]: Peraton Corp., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 8,166,000    
Investment, Identifier [Axis]: Peraton Corp., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,030,000    
Fair value, ending balance     4,030,000
Investment, Identifier [Axis]: PetSmart, LLC , Retail      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,462,000    
Fair value, ending balance     2,462,000
Investment, Identifier [Axis]: PetSmart, LLC , Retail      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,431,000    
Investment, Identifier [Axis]: PetVet Care Centers, LLC, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 30,091,000    
Fair value, ending balance 29,960,000 [7],[8],[11]   30,091,000 [9],[10],[12]
Investment, Identifier [Axis]: PetVet Care Centers, LLC, Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (68,000)    
Fair value, ending balance (65,000) [8],[13]   (68,000) [10],[14]
Investment, Identifier [Axis]: PetVet Care Centers, LLC, Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (68,000)    
Fair value, ending balance (65,000) [8],[13]   (68,000) [10],[14]
Investment, Identifier [Axis]: Pie Buyer, Inc. Food & Beverage 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 8,395,000    
Fair value, ending balance [9],[10]     8,395,000
Investment, Identifier [Axis]: Pie Buyer, Inc., Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 2,013,000    
Fair value, ending balance [10],[14]     2,013,000
Investment, Identifier [Axis]: Pie Buyer, Inc., Food & Beverage 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 2,202,000    
Fair value, ending balance 2,413,000 [8]   2,202,000 [9],[10]
Investment, Identifier [Axis]: Pie Buyer, Inc., Food & Beverage 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 2,127,000    
Investment, Identifier [Axis]: Pie Buyer, Inc., Food & Beverage 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 2,838,000    
Fair value, ending balance 8,110,000 [7],[8]   2,838,000 [9],[10],[12]
Investment, Identifier [Axis]: Pie Buyer, Inc., Food & Beverage 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 38,788,000    
Fair value, ending balance 2,759,000 [7],[8],[11]   38,788,000 [9],[10],[12]
Investment, Identifier [Axis]: Pie Buyer, Inc., Food & Beverage 5      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 37,474,000    
Investment, Identifier [Axis]: PlayPower, Inc, Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 2,909,000    
Investment, Identifier [Axis]: PlayPower, Inc. Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 17,016,000    
Fair value, ending balance [9],[10],[12]     17,016,000
Investment, Identifier [Axis]: PlayPower, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (37,000)    
Fair value, ending balance 0 [8],[13]   (37,000) [10],[14]
Investment, Identifier [Axis]: PlayPower, Inc., Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 17,175,000    
Investment, Identifier [Axis]: Pluralsight, LLC, Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 5,985,000    
Fair value, ending balance 5,985,000 [8],[20],[21]   5,985,000 [10],[18],[23]
Investment, Identifier [Axis]: Pluralsight, LLC, Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 4,551,000    
Fair value, ending balance 4,587,000 [8]   4,551,000 [10]
Investment, Identifier [Axis]: Pluralsight, LLC, Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 7,020,000    
Fair value, ending balance 7,460,000 [8]   7,020,000 [10]
Investment, Identifier [Axis]: Pluralsight, LLC, Software/Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 2,312,000    
Fair value, ending balance 2,330,000 [8]   2,312,000 [10]
Investment, Identifier [Axis]: Pluto Acquisition I, Inc, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 31,506,000    
Investment, Identifier [Axis]: Pluto Acquisition I, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 8,422,000    
Investment, Identifier [Axis]: Pluto Acquisition I, Inc. , Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 29,373,000    
Fair value, ending balance [9],[10]     29,373,000
Investment, Identifier [Axis]: Pluto Acquisition I, Inc. , Healthcare 1.1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 8,838,000    
Fair value, ending balance     8,838,000
Investment, Identifier [Axis]: Pluto Acquisition I, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,366,000    
Fair value, ending balance 3,337,000   3,366,000
Investment, Identifier [Axis]: Point Broadband Acquisition, LLC, Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23],[26] 4,758,000    
Fair value, ending balance [10],[17],[18],[23],[26]     4,758,000
Investment, Identifier [Axis]: Point Broadband Acquisition, LLC, Telecom 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 11,592,000    
Fair value, ending balance 11,592,000 [7],[8]   11,592,000 [9],[10]
Investment, Identifier [Axis]: Point Broadband Acquisition, LLC, Telecom 1.1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[19],[20],[21],[25] 4,935,000    
Investment, Identifier [Axis]: Point Broadband Acquisition, LLC, Telecom 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 27,502,000    
Fair value, ending balance 27,502,000 [7],[8]   27,502,000 [9],[10]
Investment, Identifier [Axis]: Point Broadband Acquisition, LLC, Telecom 2.1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[19],[20],[21],[25] 124,000    
Investment, Identifier [Axis]: Point Broadband Acquisition, LLC, Telecom 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23],[26] 374,000    
Fair value, ending balance [10],[17],[18],[23],[26]     374,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC , Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 5,431,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 119,233,000    
Gross additions 0    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) 0    
Fair value, ending balance 119,233,000   119,233,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC , Subordinated Debt 2      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 1,779,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 35,000,000    
Gross additions 23,000,000    
Gross reductions (23,000,000)    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) 0    
Fair value, ending balance 35,000,000   35,000,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC , Subordinated Debt 3      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 53,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,000,000    
Gross additions 6,000,000    
Gross reductions (4,030,000)    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) 30,000    
Fair value, ending balance 5,000,000   3,000,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[19],[20],[25],[32],[33] 119,233,000    
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC , Subordinated Debt 1      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 3,808,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 62,599,000    
Gross additions 14,000    
Gross reductions 0    
Realized Gain/(Loss) 0    
Change in Unrealized Gain (Loss) (13,000)    
Fair value, ending balance 62,600,000   62,599,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC), Financials 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[30],[34],[43],[44] 62,599,000    
Fair value, ending balance [10],[30],[34],[43],[44]     62,599,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     10,861,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 119,233,000 32,600,000 32,600,000
Gross additions     86,699,000
Gross reductions     142,000
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     (208,000)
Fair value, ending balance     119,233,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13],[32],[33] 5,000,000    
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[32],[33] 35,000,000    
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Financials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[26],[30],[34] 119,233,000    
Fair value, ending balance 62,600,000 [8],[32],[33]   119,233,000 [10],[17],[18],[26],[30],[34]
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Financials 3.1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14],[30],[34] 3,000,000    
Fair value, ending balance [10],[14],[30],[34]     3,000,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Financials 5      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[30],[34],[43],[44] 35,000,000    
Fair value, ending balance [10],[30],[34],[43],[44]     35,000,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Subordinated Debt 2      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     3,579,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 35,000,000 11,000,000 11,000,000
Gross additions     38,999,000
Gross reductions     (14,961,000)
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     (39,000)
Fair value, ending balance     35,000,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Subordinated Debt 3      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     117,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,000,000 0 0
Gross additions     7,000,000
Gross reductions     (4,008,000)
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     8,000
Fair value, ending balance     3,000,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Subordinated Debt 4      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     7,940,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 62,599,000 24,500,000 24,500,000
Gross additions     38,117,000
Gross reductions     63,000
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     (81,000)
Fair value, ending balance     62,599,000
Investment, Identifier [Axis]: Power Stop, LLC , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,094,000    
Investment, Identifier [Axis]: Power Stop, LLC , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,986,000    
Fair value, ending balance     2,986,000
Investment, Identifier [Axis]: Pregis TopCo, LLC , Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,708,000    
Investment, Identifier [Axis]: Pregis TopCo, LLC, Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,763,000    
Fair value, ending balance     6,763,000
Investment, Identifier [Axis]: Pretzel Parent, Inc. , Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,522,000    
Fair value, ending balance 3,450,000   3,522,000
Investment, Identifier [Axis]: Proofpoint, Inc. , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,335,000    
Fair value, ending balance 6,651,000   6,335,000
Investment, Identifier [Axis]: Pug, LLC , Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,766,000    
Fair value, ending balance 4,590,000   4,766,000
Investment, Identifier [Axis]: Questex, Inc, Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 14,777,000    
Investment, Identifier [Axis]: Questex, Inc., Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (34,000)    
Fair value, ending balance (32,000) [8],[13]   (34,000) [10],[14]
Investment, Identifier [Axis]: Questex, Inc., Media/Entertainment 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 14,837,000    
Fair value, ending balance [9],[10],[12]     14,837,000
Investment, Identifier [Axis]: Quikrete Holdings, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,019,000    
Investment, Identifier [Axis]: Quikrete Holdings, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,539,000    
Investment, Identifier [Axis]: Quikrete Holdings, Inc., Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,732,000    
Fair value, ending balance     1,732,000
Investment, Identifier [Axis]: Quikrete Holdings, Inc., Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,056,000    
Fair value, ending balance     6,056,000
Investment, Identifier [Axis]: REP TEC Intermediate Holdings, Inc., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 24,481,000    
Fair value, ending balance 24,357,000 [7],[8],[11]   24,481,000 [9],[10],[12]
Investment, Identifier [Axis]: RMP Group, Inc. , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[19],[20],[21] 320,000    
Investment, Identifier [Axis]: RMP Group, Inc., Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23] 263,000    
Fair value, ending balance [10],[17],[18],[23]     263,000
Investment, Identifier [Axis]: RSC Acquisition, Inc, Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 4,679,000    
Investment, Identifier [Axis]: RSC Acquisition, Inc, Financials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 664,000    
Investment, Identifier [Axis]: RSC Acquisition, Inc., Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 1,695,000    
Fair value, ending balance [10]     1,695,000
Investment, Identifier [Axis]: RSC Acquisition, Inc., Financials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 9,007,000    
Fair value, ending balance 8,961,000 [8]   9,007,000 [10]
Investment, Identifier [Axis]: RSC Acquisition, Inc., Financials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: RSC Acquisition, Inc., Financials 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance 0 [8],[13]   0 [10],[14]
Investment, Identifier [Axis]: RSC Acquisition, Inc., Financials 5      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 7,116,000    
Fair value, ending balance 7,080,000 [7],[8]   7,116,000 [9],[10]
Investment, Identifier [Axis]: RSC Acquisition, Inc., Financials 6      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 21,593,000    
Fair value, ending balance 21,482,000 [7],[8],[11]   21,593,000 [9],[10],[12]
Investment, Identifier [Axis]: RXB Holdings, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 9,846,000    
Investment, Identifier [Axis]: RXB Holdings, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,823,000    
Fair value, ending balance     9,823,000
Investment, Identifier [Axis]: Radar Bidco SARL , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,422,000    
Fair value, ending balance     1,422,000
Investment, Identifier [Axis]: Radiology Partners, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 11,013,000    
Investment, Identifier [Axis]: Radiology Partners, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 10,345,000    
Fair value, ending balance     10,345,000
Investment, Identifier [Axis]: Raven Acquisition Holdings, LLC , Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 9,763,000    
Investment, Identifier [Axis]: Raven Acquisition Holdings, LLC , Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance (1,000)    
Investment, Identifier [Axis]: Raven Acquisition Holdings, LLC, Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,000    
Fair value, ending balance     1,000
Investment, Identifier [Axis]: Raven Acquisition Holdings, LLC, Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,946,000    
Fair value, ending balance     7,946,000
Investment, Identifier [Axis]: Reagent Chemical and Research, LLC, Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (135,000)    
Fair value, ending balance 0 [8],[13]   (135,000) [10],[14]
Investment, Identifier [Axis]: Reagent Chemical and Research, LLC, Chemicals 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 52,128,000    
Fair value, ending balance 48,903,000 [7],[8],[11]   52,128,000 [9],[10],[12]
Investment, Identifier [Axis]: Recess Holdings, Inc. , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 7,391,000    
Investment, Identifier [Axis]: Recess Holdings, Inc., Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 12,517,000    
Fair value, ending balance     12,517,000
Investment, Identifier [Axis]: Relativity Oda, LLC, Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 7,717,000    
Fair value, ending balance 7,717,000 [7],[8],[11]   7,717,000 [9],[10],[12]
Investment, Identifier [Axis]: Renaissance Holdings Corp. , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 3,777,000    
Investment, Identifier [Axis]: Renaissance Holdings Corp., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,969,000    
Fair value, ending balance     1,969,000
Investment, Identifier [Axis]: Resolute Investment Managers, Inc. , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 2,022,000    
Fair value, ending balance 2,022,000 [8],[20],[21]   2,022,000 [10],[18],[23]
Investment, Identifier [Axis]: Resolute Investment Managers, Inc., Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,433,000    
Fair value, ending balance 991,000   2,433,000
Investment, Identifier [Axis]: Resolute Investment Managers, Inc., Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 991,000    
Fair value, ending balance     991,000
Investment, Identifier [Axis]: Revere Power, LLC, Utilities 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 8,564,000    
Fair value, ending balance     8,564,000
Investment, Identifier [Axis]: Revere Power, LLC, Utilities 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 756,000    
Fair value, ending balance     756,000
Investment, Identifier [Axis]: Rialto Management Group, LLC, Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (8,000)    
Fair value, ending balance (7,000) [8],[13]   (8,000) [10],[14]
Investment, Identifier [Axis]: Rialto Management Group, LLC, Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 21,616,000    
Fair value, ending balance 20,653,000 [7],[8],[11]   21,616,000 [9],[10],[12]
Investment, Identifier [Axis]: Roadsafe Holdings, Inc, Industrials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 1,087,000    
Fair value, ending balance [9],[10],[12]     1,087,000
Investment, Identifier [Axis]: Roadsafe Holdings, Inc., Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 7,362,000    
Fair value, ending balance 7,324,000 [7],[8]   7,362,000 [9],[10]
Investment, Identifier [Axis]: Roadsafe Holdings, Inc., Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 6,849,000    
Fair value, ending balance 6,814,000 [7],[8]   6,849,000 [9],[10]
Investment, Identifier [Axis]: Roadsafe Holdings, Inc., Industrials 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 1,081,000    
Investment, Identifier [Axis]: Roadsafe Holdings, Inc., Industrials 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 12,059,000    
Fair value, ending balance 11,994,000 [7],[8],[11]   12,059,000 [9],[10],[12]
Investment, Identifier [Axis]: Roper Industrial Products Investment Co., LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,958,000    
Investment, Identifier [Axis]: Roper Industrial Products Investment Co., LLC, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,509,000    
Fair value, ending balance     7,509,000
Investment, Identifier [Axis]: Russell Investments US Institutional Holdco, Inc., Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,544,000    
Fair value, ending balance 5,494,000   5,544,000
Investment, Identifier [Axis]: Ryan Specialty Group, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,007,000    
Fair value, ending balance 1,989,000   2,007,000
Investment, Identifier [Axis]: S&S Holdings, LLC , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,555,000    
Investment, Identifier [Axis]: S&S Holdings, LLC, Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,717,000    
Fair value, ending balance     6,717,000
Investment, Identifier [Axis]: SCIH Salt Holdings, Inc. Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (15,000)    
Investment, Identifier [Axis]: SCIH Salt Holdings, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 985,000    
Fair value, ending balance [10],[14]     985,000
Investment, Identifier [Axis]: SK Neptune Husky Finance SARL, Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 650,000    
Fair value, ending balance     650,000
Investment, Identifier [Axis]: Safety Products/JHC Acquisition Corp. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 7,332,000    
Investment, Identifier [Axis]: Safety Products/JHC Acquisition Corp., Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 399,000    
Fair value, ending balance     399,000
Investment, Identifier [Axis]: Safety Products/JHC Acquisition Corp., Industrials 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,389,000    
Fair value, ending balance     7,389,000
Investment, Identifier [Axis]: Saks Global Enterprises, LLC, Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,885,000    
Fair value, ending balance 1,470,000   2,885,000
Investment, Identifier [Axis]: Saranac CLO, Ltd. 20-8A E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,412,000    
Fair value, ending balance 1,384,000   1,412,000
Investment, Identifier [Axis]: Saturn SHC Buyer Holdings, Inc, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] (645,000)    
Investment, Identifier [Axis]: Saturn SHC Buyer Holdings, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: Saturn SHC Buyer Holdings, Inc., Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 12,993,000    
Fair value, ending balance 12,343,000 [7],[8]   12,993,000 [9],[10]
Investment, Identifier [Axis]: Saturn SHC Buyer Holdings, Inc., Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 37,165,000    
Fair value, ending balance 35,308,000 [7],[8]   37,165,000 [9],[10]
Investment, Identifier [Axis]: Saturn Sound Bidco, Ltd, Business Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14],[28] (44,000)    
Fair value, ending balance [10],[14],[28]     (44,000)
Investment, Identifier [Axis]: Saturn Sound Bidco, Ltd., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13],[27] (41,000)    
Investment, Identifier [Axis]: Saturn Sound Bidco, Ltd., Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11],[27] 24,571,000    
Investment, Identifier [Axis]: Saturn Sound Bidco, Ltd., Business Services 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12],[28] 24,212,000    
Fair value, ending balance [9],[10],[12],[28]     24,212,000
Investment, Identifier [Axis]: Sculptor CLO, Ltd. 27A E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,469,000    
Fair value, ending balance     1,469,000
Investment, Identifier [Axis]: Sedgwick Claims Management Services, Inc., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,327,000    
Fair value, ending balance 7,277,000   7,327,000
Investment, Identifier [Axis]: Sherlock Buyer Corp., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance 0 [8],[13]   0 [10],[14]
Investment, Identifier [Axis]: Sherlock Buyer Corp., Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 15,719,000    
Fair value, ending balance 15,638,000 [7],[8],[11]   15,719,000 [9],[10],[12]
Investment, Identifier [Axis]: Siena Capital Finance, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[32] 77,310,000    
Investment, Identifier [Axis]: Siena Capital Finance, LLC, Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 8,202,000   11,050,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 77,310,000 0 0
Gross additions 0   77,310,000
Gross reductions 0   127,000
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) 0   (127,000)
Fair value, ending balance 77,310,000   77,310,000
Investment, Identifier [Axis]: Siena Capital Finance, LLC, Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[30] 49,500,000    
Fair value, ending balance 54,500,000 [8],[32]   49,500,000 [10],[30]
Investment, Identifier [Axis]: Siena Capital Finance, LLC, Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[30] 77,310,000    
Fair value, ending balance [10],[18],[30]     77,310,000
Investment, Identifier [Axis]: Siena Capital Finance, LLC, Subordinated Debt      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 3,118,000   6,307,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 49,500,000 0 0
Gross additions 5,000,000   59,452,000
Gross reductions 0   (9,902,000)
Realized Gain/(Loss) 0   (14,000)
Change in Unrealized Gain (Loss) 0   (36,000)
Fair value, ending balance 54,500,000   49,500,000
Investment, Identifier [Axis]: Sierra Enterprises, LLC , Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,097,000    
Fair value, ending balance     5,097,000
Investment, Identifier [Axis]: Simplifi Holdings, Inc., Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance 1,582,000 [8],[13]   0 [10],[14]
Investment, Identifier [Axis]: Simplifi Holdings, Inc., Media/Entertainment 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 50,040,000    
Fair value, ending balance 49,782,000 [7],[8]   50,040,000 [9],[10]
Investment, Identifier [Axis]: SitusAMC Holdings Corp. , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 9,677,000    
Fair value, ending balance [10]     9,677,000
Investment, Identifier [Axis]: SitusAMC Holdings Corp., Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8],[11] 52,004,000    
Investment, Identifier [Axis]: SitusAMC Holdings Corp., Financials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 6,341,000    
Fair value, ending balance [9],[10]     6,341,000
Investment, Identifier [Axis]: Skillsoft Corp., Technology      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [23] 298,000    
Fair value, ending balance 199,000 [21]   298,000 [23]
Investment, Identifier [Axis]: Smile Brands, Inc, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 50,000    
Fair value, ending balance [10]     50,000
Investment, Identifier [Axis]: Smile Brands, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 0    
Fair value, ending balance [10],[18],[23]     0
Investment, Identifier [Axis]: Smile Brands, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] 16,000    
Investment, Identifier [Axis]: Smyrna Ready Mix Concrete, LLC, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 1,996,000    
Investment, Identifier [Axis]: Sonrava Health Holdings, LLC , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,108,000    
Fair value, ending balance     6,108,000
Investment, Identifier [Axis]: Sonrava Health Holdings, LLC, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,837,000    
Fair value, ending balance     1,837,000
Investment, Identifier [Axis]: Sonrava Health Holdings, LLC, Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 1,828,000    
Investment, Identifier [Axis]: Sonrava Health Holdings, LLC, Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 5,233,000    
Investment, Identifier [Axis]: Sotera Health Holdings, LLC , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 9,956,000    
Investment, Identifier [Axis]: Sotera Health Holdings, LLC, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,981,000    
Fair value, ending balance     9,981,000
Investment, Identifier [Axis]: Sound Point CLO, Ltd. 17-1A E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,920,000    
Fair value, ending balance     3,920,000
Investment, Identifier [Axis]: Sound Point CLO, Ltd. 17-2A E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,942,000    
Fair value, ending balance 1,588,000   1,942,000
Investment, Identifier [Axis]: Sound Point CLO, Ltd. 18-3A D, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 787,000    
Fair value, ending balance 796,000   787,000
Investment, Identifier [Axis]: Specialty Building Products Holdings, LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,807,000    
Investment, Identifier [Axis]: Specialty Building Products Holdings, LLC, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,932,000    
Fair value, ending balance     4,932,000
Investment, Identifier [Axis]: Squan Holding Corp. , Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 0    
Fair value, ending balance [10],[18],[23]     0
Investment, Identifier [Axis]: Squan Holding Corp., Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21] 0    
Investment, Identifier [Axis]: St. Croix Hospice Acquisition Corp., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 2,752,000    
Fair value, ending balance 2,738,000 [8]   2,752,000 [10]
Investment, Identifier [Axis]: St. Croix Hospice Acquisition Corp., Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 18,934,000    
Fair value, ending balance 18,839,000 [7],[8],[11]   18,934,000 [9],[10],[12]
Investment, Identifier [Axis]: St. Croix Hospice Acquisition Corp., Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[12] 24,901,000    
Fair value, ending balance 24,772,000 [7],[8],[11]   24,901,000 [10],[12]
Investment, Identifier [Axis]: Staples, Inc. , Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,580,000    
Investment, Identifier [Axis]: Staples, Inc., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,007,000    
Fair value, ending balance     7,007,000
Investment, Identifier [Axis]: Starlight Parent, LLC , Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 7,322,000    
Investment, Identifier [Axis]: Stonepeak Nile Parent, LLC , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,387,000    
Investment, Identifier [Axis]: Striper Buyer, LLC Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 16,827,000    
Fair value, ending balance [9],[10]     16,827,000
Investment, Identifier [Axis]: Striper Buyer, LLC, Paper & Packaging      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 16,739,000    
Investment, Identifier [Axis]: SunMed Group Holdings, LLC , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 12,568,000    
Fair value, ending balance [9],[10]     12,568,000
Investment, Identifier [Axis]: SunMed Group Holdings, LLC, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 0    
Investment, Identifier [Axis]: SunMed Group Holdings, LLC, Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance 12,503,000 [7],[8]   0 [10],[14]
Investment, Identifier [Axis]: Symphony CLO, Ltd. 2012-9A ER2, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,881,000    
Fair value, ending balance 2,891,000   2,881,000
Investment, Identifier [Axis]: TEI Intermediate, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 22,790,000    
Fair value, ending balance 22,794,000 [7],[8],[11]   22,790,000 [9],[10],[12]
Investment, Identifier [Axis]: TEI Intermediate, LLC, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (18,000)    
Fair value, ending balance (17,000) [8],[13]   (18,000) [10],[14]
Investment, Identifier [Axis]: TEI Intermediate, LLC, Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 358,000    
Fair value, ending balance 431,000 [8],[13]   358,000 [10],[14]
Investment, Identifier [Axis]: Tax Defense Network, LLC , Consumer 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21] 0    
Investment, Identifier [Axis]: Tax Defense Network, LLC , Consumer 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21] 0    
Investment, Identifier [Axis]: Tax Defense Network, LLC, Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[15] 404,000    
Fair value, ending balance [10],[15]     404,000
Investment, Identifier [Axis]: Tax Defense Network, LLC, Consumer 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 0    
Fair value, ending balance 0 [8],[16]   0 [10],[18],[23]
Investment, Identifier [Axis]: Tax Defense Network, LLC, Consumer 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[15] 72,000    
Fair value, ending balance 0 [8],[16]   72,000 [10],[15]
Investment, Identifier [Axis]: Tax Defense Network, LLC, Consumer 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[15] 5,342,000    
Fair value, ending balance 5,669,000 [8],[16]   5,342,000 [10],[15]
Investment, Identifier [Axis]: Tax Defense Network, LLC, Consumer 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 0    
Fair value, ending balance [10],[18],[23]     0
Investment, Identifier [Axis]: Team Health Holdings, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,649,000    
Fair value, ending balance     2,649,000
Investment, Identifier [Axis]: Tecta America Corp. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 5,502,000    
Investment, Identifier [Axis]: Tecta America Corp., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 8,803,000    
Fair value, ending balance     8,803,000
Investment, Identifier [Axis]: Tennenbaum Waterman Fund, LP, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [18],[24],[28] 5,802,000    
Fair value, ending balance 4,503,000 [20],[22],[27]   5,802,000 [18],[24],[28]
Investment, Identifier [Axis]: Tennenbaum Waterman Fund, LP, Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income 0   700,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,802,000 0 0
Gross additions 0   8,754,000
Gross reductions (1,430,000)   (2,066,000)
Realized Gain/(Loss) 0   0
Change in Unrealized Gain (Loss) 131,000   (886,000)
Fair value, ending balance 4,503,000   5,802,000
Investment, Identifier [Axis]: The NPD Group, LP, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 52,232,000    
Fair value, ending balance 0 [8],[13]   52,232,000 [9],[10]
Investment, Identifier [Axis]: The NPD Group, LP, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 573,000    
Fair value, ending balance 52,102,000 [7],[8]   573,000 [10],[14]
Investment, Identifier [Axis]: Therapy Brands Holdings, LLC , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 4,944,000    
Fair value, ending balance [9],[10]     4,944,000
Investment, Identifier [Axis]: Therapy Brands Holdings, LLC, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 5,406,000    
Fair value, ending balance 4,601,000 [7],[8]   5,406,000 [9],[10]
Investment, Identifier [Axis]: Therapy Brands Holdings, LLC, Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 4,840,000    
Investment, Identifier [Axis]: Tivity Health, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 24,537,000    
Fair value, ending balance 24,414,000 [7],[8]   24,537,000 [9],[10]
Investment, Identifier [Axis]: TransDigm, Inc. , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 5,935,000    
Investment, Identifier [Axis]: TransDigm, Inc., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,963,000    
Fair value, ending balance     5,963,000
Investment, Identifier [Axis]: Travelpro Products, Inc. , Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21],[27] 465,000    
Investment, Identifier [Axis]: Travelpro Products, Inc., Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23],[28] 751,000    
Fair value, ending balance [10],[18],[23],[28]     751,000
Investment, Identifier [Axis]: Traverse Midstream Partners, LLC , Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 12,865,000    
Investment, Identifier [Axis]: Traverse Midstream Partners, LLC, Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 12,898,000    
Fair value, ending balance     12,898,000
Investment, Identifier [Axis]: Trimaran CAVU 2021-2A, Ltd. 21-2A E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,931,000    
Fair value, ending balance     2,931,000
Investment, Identifier [Axis]: Trinity Air Consultants Holdings Corp, Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 5,878,000    
Fair value, ending balance [9],[10]     5,878,000
Investment, Identifier [Axis]: Trinity Air Consultants Holdings Corp., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance [10],[14]     0
Investment, Identifier [Axis]: Trinity Air Consultants Holdings Corp., Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 8,522,000    
Fair value, ending balance [9],[10]     8,522,000
Investment, Identifier [Axis]: Trinity Air Consultants Holdings Corp., Business Services 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 29,212,000    
Fair value, ending balance [9],[10]     29,212,000
Investment, Identifier [Axis]: Triple Lift, Inc., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (188,000)    
Fair value, ending balance (188,000) [8],[13]   (188,000) [10],[14]
Investment, Identifier [Axis]: Triple Lift, Inc., Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 37,806,000    
Fair value, ending balance 37,610,000 [7],[8],[11]   37,806,000 [9],[10],[12]
Investment, Identifier [Axis]: Triton Water Holdings, Inc. , Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 8,953,000    
Investment, Identifier [Axis]: Triton Water Holdings, Inc., Food & Beverage 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,286,000    
Fair value, ending balance     7,286,000
Investment, Identifier [Axis]: Triton Water Holdings, Inc., Food & Beverage 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,746,000    
Fair value, ending balance     1,746,000
Investment, Identifier [Axis]: Truck Hero, Inc. , Transportation 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,051,000    
Investment, Identifier [Axis]: Truck Hero, Inc. , Transportation 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 7,492,000    
Investment, Identifier [Axis]: Truck Hero, Inc., Transportation 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,492,000    
Fair value, ending balance     1,492,000
Investment, Identifier [Axis]: Truck Hero, Inc., Transportation 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 8,180,000    
Fair value, ending balance     8,180,000
Investment, Identifier [Axis]: Trysail CLO, Ltd. 21-1A E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,491,000    
Fair value, ending balance     1,491,000
Investment, Identifier [Axis]: Trystar, LLC, Utilities 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (118,000)    
Fair value, ending balance 0 [8],[13]   (118,000) [10],[14]
Investment, Identifier [Axis]: Trystar, LLC, Utilities 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (59,000)    
Fair value, ending balance 0 [8],[13]   (59,000) [10],[14]
Investment, Identifier [Axis]: Trystar, LLC, Utilities 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 10,370,000    
Fair value, ending balance 10,416,000 [7],[8],[11]   10,370,000 [9],[10],[12]
Investment, Identifier [Axis]: Trystar, LLC, Utilities 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 24,564,000    
Fair value, ending balance 24,673,000 [7],[8],[11]   24,564,000 [9],[10],[12]
Investment, Identifier [Axis]: UKG, Inc., Technology      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,772,000    
Fair value, ending balance 9,696,000   9,772,000
Investment, Identifier [Axis]: US Anesthesia Partners, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,856,000    
Investment, Identifier [Axis]: US Anesthesia Partners, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,942,000    
Fair value, ending balance     6,942,000
Investment, Identifier [Axis]: US Oral Surgery Management Holdco, LLC , Healthcare 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 17,668,000    
Fair value, ending balance [9],[10]     17,668,000
Investment, Identifier [Axis]: US Oral Surgery Management Holdco, LLC, Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 5,050,000    
Fair value, ending balance 5,050,000 [8]   5,050,000 [10]
Investment, Identifier [Axis]: US Oral Surgery Management Holdco, LLC, Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance 0 [8],[13]   0 [10],[14]
Investment, Identifier [Axis]: US Oral Surgery Management Holdco, LLC, Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 6,997,000    
Fair value, ending balance 6,997,000 [7],[8]   6,997,000 [9],[10]
Investment, Identifier [Axis]: US Oral Surgery Management Holdco, LLC, Healthcare 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 6,098,000    
Fair value, ending balance 6,098,000 [7],[8]   6,098,000 [9],[10]
Investment, Identifier [Axis]: US Oral Surgery Management Holdco, LLC, Healthcare 4      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 17,668,000    
Investment, Identifier [Axis]: US Salt Investors, LLC, Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance 0 [8],[13]   0 [10],[14]
Investment, Identifier [Axis]: US Salt Investors, LLC, Chemicals 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 27,311,000    
Fair value, ending balance 26,794,000 [7],[8]   27,311,000 [9],[10]
Investment, Identifier [Axis]: United Airlines, Inc. , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 3,731,000    
Investment, Identifier [Axis]: United Airlines, Inc., Transportation 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,966,000    
Fair value, ending balance     1,966,000
Investment, Identifier [Axis]: United Airlines, Inc., Transportation 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,755,000    
Fair value, ending balance     3,755,000
Investment, Identifier [Axis]: University Support Services, LLC , Education      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,294,000    
Fair value, ending balance     7,294,000
Investment, Identifier [Axis]: University Support Services, LLC, Education      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 5,042,000    
Investment, Identifier [Axis]: Urban One, Inc., Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [18] 972,000    
Fair value, ending balance 876,000 [20]   972,000 [18]
Investment, Identifier [Axis]: VS Buyer, LLC, Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,074,000    
Fair value, ending balance     1,074,000
Investment, Identifier [Axis]: Varicent Intermediate Holdings Corp., Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 19,113,000    
Fair value, ending balance 20,143,000 [7],[8],[11]   19,113,000 [9],[10],[12]
Investment, Identifier [Axis]: Varicent Intermediate Holdings Corp., Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (63,000)    
Fair value, ending balance (50,000) [8],[13]   (63,000) [10],[14]
Investment, Identifier [Axis]: Varicent Intermediate Holdings Corp., Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (35,000)    
Fair value, ending balance (33,000) [8],[13]   (35,000) [10],[14]
Investment, Identifier [Axis]: Venga Finance SARL, Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,925,000    
Fair value, ending balance 3,888,000   3,925,000
Investment, Identifier [Axis]: Venture CDO, Ltd. 16-23A ER2, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,806,000    
Fair value, ending balance 2,612,000   2,806,000
Investment, Identifier [Axis]: Venture CLO 43, Ltd. 21-43A E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,807,000    
Fair value, ending balance 2,774,000   2,807,000
Investment, Identifier [Axis]: Venture Global Calcasieu Pass, LLC, Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,621,000    
Investment, Identifier [Axis]: Venture Global LNG, Inc., Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 4,863,000    
Investment, Identifier [Axis]: Victors CCC Buyer, LLC , Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 23,698,000    
Fair value, ending balance [9],[10]     23,698,000
Investment, Identifier [Axis]: Victors CCC Buyer, LLC, Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 1,567,000    
Fair value, ending balance 1,559,000 [8]   1,567,000 [10]
Investment, Identifier [Axis]: Victors CCC Buyer, LLC, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 0    
Fair value, ending balance 0 [8],[13]   0 [10],[14]
Investment, Identifier [Axis]: Victors CCC Buyer, LLC, Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 23,577,000    
Investment, Identifier [Axis]: Victory Buyer, LLC , Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 9,258,000    
Investment, Identifier [Axis]: Victory Buyer, LLC, Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 43,690,000    
Fair value, ending balance 44,610,000 [7],[8]   43,690,000 [9],[10]
Investment, Identifier [Axis]: Victory Buyer, LLC, Industrials 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,253,000    
Fair value, ending balance     9,253,000
Investment, Identifier [Axis]: Virgin Media Bristol, LLC , Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,472,000    
Fair value, ending balance     2,472,000
Investment, Identifier [Axis]: WCG Purchaser Corp. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 6,421,000    
Investment, Identifier [Axis]: WCG Purchaser Corp., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,938,000    
Fair value, ending balance     4,938,000
Investment, Identifier [Axis]: WEC US Holdings, Ltd., Utilities      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,505,000    
Fair value, ending balance     5,505,000
Investment, Identifier [Axis]: WHCG Purchaser III, Inc. , Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[15] 8,738,000    
Fair value, ending balance 0 [8],[20],[21]   8,738,000 [10],[15]
Investment, Identifier [Axis]: WHCG Purchaser III, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10] 22,824,000    
Fair value, ending balance 9,176,000 [8],[16]   22,824,000 [10]
Investment, Identifier [Axis]: WHCG Purchaser III, Inc., Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 0    
Fair value, ending balance 23,448,000 [8]   0 [10],[18],[23]
Investment, Identifier [Axis]: WIN Holdings III Corp.), Consumer 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 10,016,000    
Fair value, ending balance [9],[10]     10,016,000
Investment, Identifier [Axis]: WIN Holdings III Corp., Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 1,986,000    
Fair value, ending balance [10],[14]     1,986,000
Investment, Identifier [Axis]: WIN Holdings III Corp., Consumer 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 41,683,000    
Fair value, ending balance 1,986,000 [8],[13]   41,683,000 [9],[10]
Investment, Identifier [Axis]: WIN Holdings III Corp., Consumer 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 41,683,000    
Investment, Identifier [Axis]: WIN Holdings III Corp., Consumer 3      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [7],[8] 9,965,000    
Investment, Identifier [Axis]: WPNT, LLC , Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[19],[20],[21],[32] 0    
Investment, Identifier [Axis]: WPNT, LLC, Equity/Other Investments      
Investments in and Advances to Affiliates [Line Items]      
Amount of dividends and interest included in income     0
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 0 $ 0 0
Gross additions     0
Gross reductions     0
Realized Gain/(Loss)     0
Change in Unrealized Gain (Loss)     0
Fair value, ending balance     0
Investment, Identifier [Axis]: WPNT, LLC, Media/Entertainment      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[17],[18],[23],[30] 0    
Fair value, ending balance [10],[17],[18],[23],[30]     0
Investment, Identifier [Axis]: WaterBridge Midstream Operating, LLC , Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 12,728,000    
Investment, Identifier [Axis]: WaterBridge Midstream Operating, LLC, Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 9,921,000    
Fair value, ending balance     9,921,000
Investment, Identifier [Axis]: Waterbridge NDB Operating, LLC , Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,081,000    
Investment, Identifier [Axis]: Waterbridge NDB Operating, LLC, Energy      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,990,000    
Fair value, ending balance     2,990,000
Investment, Identifier [Axis]: Watlow Electric Manufacturing, Co., Industrials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 4,646,000    
Fair value, ending balance     4,646,000
Investment, Identifier [Axis]: Waystar Technologies, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,326,000    
Fair value, ending balance     1,326,000
Investment, Identifier [Axis]: West Coast Dental Services, Inc. Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 2,740,000    
Fair value, ending balance [10],[14]     2,740,000
Investment, Identifier [Axis]: West Coast Dental Services, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 3,575,000    
Investment, Identifier [Axis]: West Coast Dental Services, Inc., Healthcare 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 27,503,000    
Fair value, ending balance 27,595,000 [7],[8]   27,503,000 [9],[10]
Investment, Identifier [Axis]: West Coast Dental Services, Inc., Healthcare 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10] 1,648,000    
Fair value, ending balance 1,648,000 [7],[8]   1,648,000 [9],[10]
Investment, Identifier [Axis]: WestJet Loyalty, LP , Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 5,725,000    
Investment, Identifier [Axis]: WestJet Loyalty, LP, Transportation      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 5,774,000    
Fair value, ending balance     5,774,000
Investment, Identifier [Axis]: Westwood Professional Services, Inc, Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] 3,050,000    
Fair value, ending balance [10],[14]     3,050,000
Investment, Identifier [Axis]: Westwood Professional Services, Inc., Business Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [9],[10],[12] 44,868,000    
Fair value, ending balance 45,075,000 [7],[8],[11]   44,868,000 [9],[10],[12]
Investment, Identifier [Axis]: Westwood Professional Services, Inc., Business Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 4,454,000    
Investment, Identifier [Axis]: Westwood Professional Services, Inc., Business Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[14] (65,000)    
Fair value, ending balance 0 [8],[13]   (65,000) [10],[14]
Investment, Identifier [Axis]: White Cap Supply Holdings, LLC, Consumer      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 6,843,000    
Fair value, ending balance 5,270,000   6,843,000
Investment, Identifier [Axis]: Whitehorse, Ltd. 14-1A E, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[28] 821,000    
Fair value, ending balance 406,000 [8],[20],[27]   821,000 [10],[18],[28]
Investment, Identifier [Axis]: Wind River CLO, Ltd. 14-2A FR, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 855,000    
Fair value, ending balance 497,000   855,000
Investment, Identifier [Axis]: Windsor Holdings III, LLC , Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 3,260,000    
Investment, Identifier [Axis]: Windsor Holdings III, LLC , Chemicals      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 3,312,000    
Fair value, ending balance     3,312,000
Investment, Identifier [Axis]: World Business Lenders, LLC , Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[20],[21] 1,405,000    
Investment, Identifier [Axis]: World Business Lenders, LLC, Financials      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 1,405,000    
Fair value, ending balance [10],[18],[23]     1,405,000
Investment, Identifier [Axis]: X Corp. , Media/Entertainment 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 2,429,000    
Investment, Identifier [Axis]: X Corp. , Media/Entertainment 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 9,710,000    
Investment, Identifier [Axis]: YummyEarth, Inc., Food & Beverage      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[18],[23] 0    
Fair value, ending balance 0 [8],[20],[21]   0 [10],[18],[23]
Investment, Identifier [Axis]: Zais CLO 13, Ltd. 19-13A D1, Diversified Investment Vehicles      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 2,915,000    
Fair value, ending balance     2,915,000
Investment, Identifier [Axis]: Zayo Group Holdings, Inc , Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 1,509,000    
Investment, Identifier [Axis]: Zayo Group Holdings, Inc. , Telecom      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance 7,982,000    
Investment, Identifier [Axis]: Zayo Group Holdings, Inc., Telecom 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,483,000    
Fair value, ending balance     1,483,000
Investment, Identifier [Axis]: Zayo Group Holdings, Inc., Telecom 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 7,859,000    
Fair value, ending balance     7,859,000
Investment, Identifier [Axis]: Zelis Cost Management Buyer, Inc., Healthcare      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance 1,867,000    
Fair value, ending balance     1,867,000
Investment, Identifier [Axis]: Zendesk, Inc. Software/Services      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, beginning balance [10],[43],[44] 65,525,000    
Fair value, ending balance [10],[43],[44]     $ 65,525,000
Investment, Identifier [Axis]: Zendesk, Inc., Software/Services 1      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8],[13] 5,010,000    
Investment, Identifier [Axis]: Zendesk, Inc., Software/Services 2      
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]      
Fair value, ending balance [8] $ 65,204,000    
[1] Percentages are based on net assets attributable to common stock as of December 31, 2024.
[2] Unless otherwise indicated, all investments in the consolidated schedules of investments are non-affiliated, non-controlled investments.
[3] Unless otherwise indicated, all of the Company's investments or a portion thereof are pledged as collateral under the JPM Revolver Facility.
[4] Percentages are based on net assets attributable to common stock as of June 30, 2025.
[5] Unless otherwise indicated, all investments in the consolidated schedules of investments are non-affiliated, non-controlled investments.
[6] Unless otherwise indicated, all of the Company's investments or a portion thereof are pledged as collateral under the JPM Revolver Facility.
[7] The Company's investment or a portion thereof is pledged as collateral under the JPM Credit Facility.
[8] The fair value of investments with respect to securities for which market quotations are not readily available is determined in good faith by the Company's Board of Directors (as defined below) as required by the 1940 Act. Such investments are valued using significant unobservable inputs (See Note 3 to the consolidated financial statements).
[9] The Company's investment or a portion thereof is pledged as collateral under the JPM Credit Facility.
[10] The fair value of investments with respect to securities for which market quotations are not readily available is determined in good faith by the Company's Board of Directors (as defined below) as required by the 1940 Act. Such investments are valued using significant unobservable inputs (See Note 3 to the consolidated financial statements).
[11] The Company's investment or a portion thereof is pledged as collateral under the Wells Fargo Credit Facility. Individual investments can be divided into parts which are pledged to separate credit facilities.
[12] The Company's investment or a portion thereof is pledged as collateral under the Wells Fargo Credit Facility. Individual investments can be divided into parts which are pledged to separate credit facilities.
[13] Position or portion thereof is an unfunded loan commitment, and no interest is being earned on the unfunded portion. The investment may be subject to an unused/letter of credit facility fee. The negative fair value, if applicable, is the result of the capitalized discount on the loan or the unfunded commitment being valued below par. The negative amortized cost, if applicable, is the result of the capitalized discount being greater than the principal amount outstanding on the loan. Please refer to Note 7 - Commitments and Contingencies for additional details.
[14] Position or portion thereof is an unfunded loan commitment, and no interest is being earned on the unfunded portion. The investment may be subject to an unused/letter of credit facility fee. The negative fair value, if applicable, is the result of the capitalized discount on the loan or the unfunded commitment being valued below par. The negative amortized cost, if applicable, is the result of the capitalized discount being greater than the principal amount outstanding on the loan. Please refer to Note 7 - Commitments and Contingencies for additional details.
[15] The investment is on non-accrual status as of December 31, 2024.
[16] The investment is on non-accrual status as of June 30, 2025. As of June 30, 2025, $30.0 million of the cost and $13.2 million of fair value of MGTF Radio Company, LLC is considered to be on non-accrual status.
[17] Investments are held in the taxable wholly-owned, consolidated subsidiary, 54th Street Equity Holdings, Inc.
[18] Securities exempt from registration under the Securities Act of 1933 (as defined below), and may be deemed to be “restricted securities”. As of December 31, 2024, the aggregate fair value of these securities is $688.5 million or 36.0% of the Company’s net assets. The initial acquisition dates have been included for such securities.
[19] Investments are held in the taxable wholly-owned, consolidated subsidiary, 54th Street Equity Holdings, Inc.
[20] Securities exempt from registration under the Securities Act of 1933 (as defined below), and may be deemed to be “restricted securities”. As of June 30, 2025, the aggregate fair value of these securities is $580.2 million or 31.3% of the Company’s net assets. The initial acquisition dates have been included for such securities.
[21] Non-income producing at June 30, 2025.
[22] The provisions of the 1940 Act classify investments further based on the level of ownership that the Company maintains in a particular portfolio company. As defined in the 1940 Act, a company is generally deemed as "non-affiliated" when the Company owns less than 5% of a portfolio company's outstanding voting securities and "affiliated" when the Company owns 5% or more of a portfolio company's outstanding voting securities. The Company classifies this investment as "affiliated".
[23] Non-income producing at December 31, 2024.
[24] The provisions of the 1940 Act classify investments further based on the level of ownership that the Company maintains in a particular portfolio company. As defined in the 1940 Act, a company is generally deemed as "non-affiliated" when the Company owns less than 5% of a portfolio company's outstanding voting securities and "affiliated" when the Company owns 5% or more of a portfolio company's outstanding voting securities. The Company classifies this investment as "affiliated".
[25] Investments are held in the taxable wholly-owned, consolidated subsidiary, FBCC EEF Holdings LLC.
[26] Investments are held in the taxable wholly-owned, consolidated subsidiary, FBCC EEF Holdings LLC.
[27] All of the Company's investments, except the investments noted by this footnote, are qualifying assets under Section 55(a) of the Investment Company Act of 1940, as amended (the "1940 Act"). Under the 1940 Act, the Company may not acquire any non-qualifying asset unless, at the time the acquisition is made, qualifying assets represent at least 70% of the Company's total assets. At June 30, 2025, qualifying assets represent 90.8% of the Company's total assets.
[28] All of the Company's investments, except the investments noted by this footnote, are qualifying assets under Section 55(a) of the Investment Company Act of 1940, as amended (the "1940 Act"). Under the 1940 Act, the Company may not acquire any non-qualifying asset unless, at the time the acquisition is made, qualifying assets represent at least 70% of the Company's total assets. At December 31, 2024, qualifying assets represent 88.5% of the Company's total assets.
[29] The Company's investment is held through the consolidated subsidiary, Kahala Aviation Holdings, LLC, which owns 49% of the operating company, Danish CRJ LTD.
[30] The provisions of the 1940 Act classify investments based on the level of control that the Company maintains in a particular portfolio company. As defined in the 1940 Act, a company is generally presumed to be “non-controlled” when the Company owns 25% or less of the portfolio company’s outstanding voting securities and/or does not have the power to exercise control over the management or policies of such portfolio company. A company is generally presumed to be “controlled” when the Company owns more than 25% of the portfolio company’s outstanding voting securities and/or has the power to exercise control over the management or policies of such portfolio company. The Company classifies this investment as “controlled”.
[31] The Company's investment is held through the consolidated subsidiary, Kahala Aviation Holdings, LLC, which owns 49% of the operating company, Danish CRJ LTD.
[32] The provisions of the 1940 Act classify investments based on the level of control that the Company maintains in a particular portfolio company. As defined in the 1940 Act, a company is generally presumed to be “non-controlled” when the Company owns 25% or less of the portfolio company’s outstanding voting securities and/or does not have the power to exercise control over the management or policies of such portfolio company. A company is generally presumed to be “controlled” when the Company owns more than 25% of the portfolio company’s outstanding voting securities and/or has the power to exercise control over the management or policies of such portfolio company. The Company classifies this investment as “controlled”.
[33] The Company's investment falls under the definition of a significant subsidiary, as it exceeded the threshold of at least one of the tests under Rule 4-08(g), or exceeded the threshold of at least one of the tests under Rule 3-09. See Note 3 for summarized financial information.
[34] The Company's investment falls under the definition of a significant subsidiary, as it exceeded the threshold of at least one of the tests under Rule 4-08(g), or exceeded the threshold of at least one of the tests under Rule 3-09. See Note 3 for summarized financial information.
[35] The Company's investment is held through the consolidated subsidiaries, Kahala Aviation Holdings, LLC and Kahala Aviation US, Inc., which own 100% of the equity of the operating company, Kahala US OpCo LLC.
[36] The Company's investment is held through the consolidated subsidiary, Kahala Aviation Holdings, LLC, which owns 100% of the equity of the operating company, Kahala Aviation, LLC.
[37] The Company's investment is held through the consolidated subsidiaries, Kahala Aviation Holdings, LLC and Kahala Aviation US, Inc., which own 100% of the equity of the operating company, Kahala US OpCo LLC.
[38] The Company's investment is held through the consolidated subsidiary, Kahala Aviation Holdings, LLC, which owns 100% of the equity of the operating company, Kahala Aviation, LLC.
[39] The investment is held through BSP TCAP Acquisition Holdings LP, which is an affiliated acquisition entity. Due to certain restrictions, such as limits on the number of partners allowable within the equity structures of the newly acquired investments, these investments are still held within the acquisition entity as of December 31, 2024
[40] The investment is held through BSP TCAP Acquisition Holdings LP, which is an affiliated acquisition entity. Due to certain restrictions, such as limits on the number of partners allowable within the equity structures of the newly acquired investments, these investments are still held within the acquisition entity as of June 30, 2025.
[41] The Collateralized Securities - subordinated notes are treated as equity investments and are entitled to recurring distributions which are generally equal to the remaining cash flow of the payments made by the underlying fund’s securities less contractual payments to debt holders and fund expenses. The estimated yield indicated is based upon a current projection of the amount and timing of these recurring distributions and the estimated amount of repayment of principal upon termination. Such projections are periodically reviewed and adjusted, and the estimated yield may not ultimately be realized.
[42] The Collateralized Securities - subordinated notes are treated as equity investments and are entitled to recurring distributions which are generally equal to the remaining cash flow of the payments made by the underlying fund’s securities less contractual payments to debt holders and fund expenses. The estimated yield indicated is based upon a current projection of the amount and timing of these recurring distributions and the estimated amount of repayment of principal upon termination. Such projections are periodically reviewed and adjusted, and the estimated yield may not ultimately be realized.
[43] 40% of the Company’s investment is pledged as collateral under the total return swap agreement with Nomura.
[44] The Company’s investment or a portion thereof is held through a total return swap agreement with Nomura Global Financial Products Inc. (“Nomura”).