v3.26.1
Schedules of Investments and Advances to Affiliates (Details) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [1],[2],[3]     $ 4,071,008,000    
Fair value, ending balance $ 4,079,384,000 [4],[5],[6]   4,079,384,000 [4],[5],[6]   $ 4,071,008,000 [1],[2],[3]
Net change in deferred taxes (2,981,000) $ (1,684,000) (23,000) $ (3,731,000) (6,100,000)
Total Control Investments          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     35,539,000   76,091,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     686,505,000 785,556,000 785,556,000
Gross additions     63,446,000   142,549,000
Gross reductions     (44,731,000)   (222,647,000)
Realized Gain/(Loss)     (33,029,000)   (134,000)
Change in Unrealized Gain (Loss)     45,896,000   (18,819,000)
Fair value, ending balance 718,087,000   718,087,000   686,505,000
Total Affiliate Investments          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     1,259,000   2,996,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     49,827,000 35,596,000 35,596,000
Gross additions     595,000   30,865,000
Gross reductions     (18,738,000)   (8,345,000)
Realized Gain/(Loss)     79,000   15,000
Change in Unrealized Gain (Loss)     (1,299,000)   (8,304,000)
Fair value, ending balance 30,464,000   30,464,000   49,827,000
Total Control & Affiliate Investments          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     36,798,000   79,087,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     736,332,000 821,152,000 821,152,000
Gross additions     64,041,000   173,414,000
Gross reductions     (63,469,000)   (230,992,000)
Realized Gain/(Loss)     (32,950,000)   (119,000)
Change in Unrealized Gain (Loss)     44,597,000   (27,123,000)
Fair value, ending balance 748,551,000   748,551,000   736,332,000
Investment, Affiliated Issuer, No Longer Held          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     7,900   117,100
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Realized Gain/(Loss)     (32,900,000)   15,200
Change in Unrealized Gain (Loss)     33,600,000   (20,100)
Investment, Identifier [Axis]: 1236904 BC, Ltd. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     3,511,000    
Fair value, ending balance 581,000 [9],[10]   581,000 [9],[10]   3,511,000 [7],[8]
Investment, Identifier [Axis]: 1236904 BC, Ltd. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     4,588,000    
Fair value, ending balance 4,436,000 [9],[10],[12]   4,436,000 [9],[10],[12]   4,588,000 [7],[8],[11]
Investment, Identifier [Axis]: AAdvantage Loyalty IP, Ltd., Passenger Airlines          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,997,000    
Fair value, ending balance 3,963,000   3,963,000   3,997,000
Investment, Identifier [Axis]: ACE Solutions, LLC | Oil, Gas & Consumable Fuels 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (45,000)   (45,000)    
Investment, Identifier [Axis]: ACE Solutions, LLC | Oil, Gas & Consumable Fuels 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 7,412,000   7,412,000    
Investment, Identifier [Axis]: ACE Solutions, LLC | Oil, Gas & Consumable Fuels 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 10,373,000   10,373,000    
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC | Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 17,205,000   17,205,000    
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     123,000    
Fair value, ending balance 113,000 [10]   113,000 [10]   123,000 [8]
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     243,000    
Fair value, ending balance 1,037,000 [10],[13]   1,037,000 [10],[13]   243,000 [8],[14]
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC | Health Care Providers & Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     3,825,000    
Fair value, ending balance 3,527,000 [9],[10]   3,527,000 [9],[10]   3,825,000 [7],[8]
Investment, Identifier [Axis]: ADCS Clinics Intermediate Holdings, LLC | Health Care Providers & Services 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     18,658,000    
Fair value, ending balance [7],[8]         18,658,000
Investment, Identifier [Axis]: ADMI Corp., Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,669,000    
Fair value, ending balance 2,602,000   2,602,000   2,669,000
Investment, Identifier [Axis]: AIG CLO, Ltd. 21-1A F, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,320,000    
Fair value, ending balance 1,320,000   1,320,000   1,320,000
Investment, Identifier [Axis]: ARC Falcon I, Inc., Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,955,000    
Fair value, ending balance         4,955,000
Investment, Identifier [Axis]: Accel International Holdings, LLC | Electrical Equipment 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (21,000)    
Fair value, ending balance 952,000 [10],[13]   952,000 [10],[13]   (21,000) [8],[14]
Investment, Identifier [Axis]: Accel International Holdings, LLC | Electrical Equipment 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     27,560,000    
Fair value, ending balance 27,685,000 [9],[10],[12]   27,685,000 [9],[10],[12]   27,560,000 [7],[8],[11]
Investment, Identifier [Axis]: Acrisure, LLC, Insurance          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,154,000    
Fair value, ending balance 4,622,000   4,622,000   5,154,000
Investment, Identifier [Axis]: Adelaide Borrower, LLC | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Adelaide Borrower, LLC | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     898,000    
Fair value, ending balance 399,000 [10],[13]   399,000 [10],[13]   898,000 [8],[14]
Investment, Identifier [Axis]: Adelaide Borrower, LLC | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     35,895,000    
Fair value, ending balance 35,895,000 [9],[10],[12]   35,895,000 [9],[10],[12]   35,895,000 [7],[8],[11]
Investment, Identifier [Axis]: Adtalem Global Education, Inc., Diversified Consumer Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     238,000    
Fair value, ending balance         238,000
Investment, Identifier [Axis]: Advanced Integration Technology, LP | Aerospace & Defense          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 12,144,000   12,144,000    
Investment, Identifier [Axis]: Alera Group, Inc. | Insurance          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[11]     22,528,000    
Fair value, ending balance 21,063,000 [9],[12]   21,063,000 [9],[12]   22,528,000 [7],[11]
Investment, Identifier [Axis]: Alera Group, Inc., Insurance          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,794,000    
Fair value, ending balance 7,325,000   7,325,000   7,794,000
Investment, Identifier [Axis]: Allwyn Entertainment Financing US, LLC, Hotels, Restaurants & Leisure          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,860,000    
Fair value, ending balance 6,886,000   6,886,000   6,860,000
Investment, Identifier [Axis]: American Auto Auction Group, LLC, Commercial Services & Supplies          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 1,986,000   1,986,000    
Investment, Identifier [Axis]: American Rock Salt Company, LLC | Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 5,276,000   5,276,000    
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 [7]     1,516,000    
Fair value, ending balance 1,791,000 [9]   1,791,000 [9]   1,516,000 [7]
Investment, Identifier [Axis]: American Rock Salt Company, LLC | Chemicals 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     4,855,000    
Fair value, ending balance [7],[8]         4,855,000
Investment, Identifier [Axis]: American Rock Salt Company, LLC, Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,570,000    
Fair value, ending balance 1,706,000   1,706,000   1,570,000
Investment, Identifier [Axis]: Amylu Borrower Sub, LLC | Food Products 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 1,135,000 [10],[13]   1,135,000 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Amylu Borrower Sub, LLC | Food Products 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Amylu Borrower Sub, LLC | Food Products 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     39,436,000    
Fair value, ending balance 39,237,000 [9],[10]   39,237,000 [9],[10]   39,436,000 [7],[8]
Investment, Identifier [Axis]: Aprio Advisory Group, LLC | Financial Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (112,000)    
Fair value, ending balance 655,000 [10],[13]   655,000 [10],[13]   (112,000) [8],[14]
Investment, Identifier [Axis]: Aprio Advisory Group, LLC | Financial Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (9,000)    
Fair value, ending balance (8,000) [10],[13]   (8,000) [10],[13]   (9,000) [8],[14]
Investment, Identifier [Axis]: Arch Global Precision, LLC | Machinery 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     938,000    
Fair value, ending balance 2,194,000 [10]   2,194,000 [10]   938,000 [8],[14]
Investment, Identifier [Axis]: Arch Global Precision, LLC | Machinery 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     2,241,000    
Fair value, ending balance 887,000 [10],[13]   887,000 [10],[13]   2,241,000 [8]
Investment, Identifier [Axis]: Arch Global Precision, LLC | Machinery 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     7,112,000    
Fair value, ending balance 6,962,000 [9],[10],[12]   6,962,000 [9],[10],[12]   7,112,000 [7],[8],[11]
Investment, Identifier [Axis]: Arches Buyer, Inc., Media          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,923,000    
Fair value, ending balance 5,860,000   5,860,000   5,923,000
Investment, Identifier [Axis]: Arcline FM Holdings, LLC, Aerospace & Defense          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,989,000    
Fair value, ending balance 4,963,000   4,963,000   4,989,000
Investment, Identifier [Axis]: Arctic Holdco, LLC | Trading Companies & Distributors 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     3,243,000    
Fair value, ending balance 5,224,000 [10]   5,224,000 [10]   3,243,000 [8],[14]
Investment, Identifier [Axis]: Arctic Holdco, LLC | Trading Companies & Distributors 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     632,000    
Fair value, ending balance 984,000 [10],[13]   984,000 [10],[13]   632,000 [8],[14]
Investment, Identifier [Axis]: Arctic Holdco, LLC | Trading Companies & Distributors 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     45,922,000    
Fair value, ending balance 45,690,000 [9],[10],[12]   45,690,000 [9],[10],[12]   45,922,000 [7],[8],[11]
Investment, Identifier [Axis]: Armada Parent, Inc. | Aerospace & Defense 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     3,841,000    
Fair value, ending balance 3,822,000 [10]   3,822,000 [10]   3,841,000 [8]
Investment, Identifier [Axis]: Armada Parent, Inc. | Aerospace & Defense 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Armada Parent, Inc. | Aerospace & Defense 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     55,492,000    
Fair value, ending balance 55,213,000 [9],[10]   55,213,000 [9],[10]   55,492,000 [7],[8]
Investment, Identifier [Axis]: Artera Services, LLC, Construction & Engineering          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,440,000    
Fair value, ending balance 4,843,000   4,843,000   4,440,000
Investment, Identifier [Axis]: Artifact Bidco, Inc. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Artifact Bidco, Inc. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Artifact Bidco, Inc. | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     10,875,000    
Fair value, ending balance 10,875,000 [9],[10],[12]   10,875,000 [9],[10],[12]   10,875,000 [7],[8],[11]
Investment, Identifier [Axis]: Ascend Learning, LLC , Diversified Consumer Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,984,000    
Fair value, ending balance 3,852,000   3,852,000   3,984,000
Investment, Identifier [Axis]: Ascensus Group Holdings, Inc. | Financial Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     16,600,000    
Fair value, ending balance 16,765,000   16,765,000   16,600,000 [8]
Investment, Identifier [Axis]: Ascensus Group Holdings, Inc., Financial Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,472,000    
Fair value, ending balance 7,282,000   7,282,000   7,472,000
Investment, Identifier [Axis]: Athenahealth Group, Inc., Health Care Technology          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     9,935,000    
Fair value, ending balance 7,814,000   7,814,000   9,935,000
Investment, Identifier [Axis]: Athletico Management, LLC, Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,577,000    
Fair value, ending balance         3,577,000
Investment, Identifier [Axis]: AuditBoard, Inc. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     10,898,000    
Fair value, ending balance 10,735,000 [10]   10,735,000 [10]   10,898,000 [8]
Investment, Identifier [Axis]: AuditBoard, Inc. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [14]     0    
Fair value, ending balance (65,000) [10],[13]   (65,000) [10],[13]   0 [14]
Investment, Identifier [Axis]: AuditBoard, Inc. | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     22,887,000    
Fair value, ending balance 22,544,000 [9],[10]   22,544,000 [9],[10]   22,887,000 [7],[8]
Investment, Identifier [Axis]: AuditBoard, Inc. | Software 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     5,742,000    
Fair value, ending balance 5,655,000 [9],[10]   5,655,000 [9],[10]   5,742,000 [7],[8]
Investment, Identifier [Axis]: Avalara, Inc, Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,992,000    
Fair value, ending balance         5,992,000
Investment, Identifier [Axis]: Aventine Holdings, LLC | Entertainment          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     41,466,000    
Fair value, ending balance 36,847,000 [10],[15]   36,847,000 [10],[15]   41,466,000 [7],[8]
Investment, Identifier [Axis]: Aventine Holdings, LLC | Entertainment 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     9,809,000    
Fair value, ending balance 9,982,000 [10]   9,982,000 [10]   9,809,000 [7],[8]
Investment, Identifier [Axis]: Aventine Holdings, LLC | Entertainment 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     24,777,000    
Fair value, ending balance 24,529,000 [10],[12]   24,529,000 [10],[12]   24,777,000 [7],[8],[11]
Investment, Identifier [Axis]: Axiom Global, Inc. | Professional Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     46,659,000    
Fair value, ending balance 46,421,000 [9],[10],[12]   46,421,000 [9],[10],[12]   46,659,000 [7],[8],[11]
Investment, Identifier [Axis]: Azurite Intermediate Holdings, Inc. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     22,639,000    
Fair value, ending balance 22,018,000 [10]   22,018,000 [10]   22,639,000 [8]
Investment, Identifier [Axis]: Azurite Intermediate Holdings, Inc. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 9,688,000 [10]   9,688,000 [10]   0 [8],[14]
Investment, Identifier [Axis]: Azurite Intermediate Holdings, Inc. | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     9,961,000    
Fair value, ending balance (91,000) [10],[13]   (91,000) [10],[13]   9,961,000 [8]
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc. | Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[11],[16],[17],[18]     12,528,000    
Fair value, ending balance 12,529,000 [10],[19],[20],[21]   12,529,000 [10],[19],[20],[21]   12,528,000 [8],[11],[16],[17],[18]
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc. | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14],[18]     0    
Fair value, ending balance 3,433,000 [10],[21]   3,433,000 [10],[21]   0 [8],[14],[18]
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc. | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[18]     4,984,000    
Fair value, ending balance 5,330,000 [10],[21]   5,330,000 [10],[21]   4,984,000 [8],[18]
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc. | Health Care Providers & Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[18]     8,307,000    
Fair value, ending balance 8,884,000 [10],[21]   8,884,000 [10],[21]   8,307,000 [8],[18]
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc. | Health Care Providers & Services 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[21] 4,346,000   4,346,000    
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc., Equity/Other Investments          
Schedule of Investments [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     12,528,000 0 0
Gross additions     0   12,528,000
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     1,000   0
Fair value, ending balance 12,529,000   12,529,000   12,528,000
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc., Senior Secured First Lien Debt          
Schedule of Investments [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]: BCPE Oceandrive Buyer, Inc., Senior Secured First Lien Debt 1          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     124,000   12,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     0 0 0
Gross additions     3,441,000   169,000
Gross reductions     (83,000)   (246,000)
Realized Gain/(Loss)     0   (86,000)
Change in Unrealized Gain (Loss)     75,000   163,000
Fair value, ending balance 3,433,000   3,433,000   0
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc., Senior Secured First Lien Debt 2          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     434,000   146,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     8,307,000 0 0
Gross additions     577,000   8,307,000
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     0   0
Fair value, ending balance 8,884,000   8,884,000   8,307,000
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc., Senior Secured First Lien Debt 3          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     193,000   235,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,984,000 0 0
Gross additions     346,000   10,109,000
Gross reductions     0   (5,373,000)
Realized Gain/(Loss)     0   248,000
Change in Unrealized Gain (Loss)     0   0
Fair value, ending balance 5,330,000   5,330,000   4,984,000
Investment, Identifier [Axis]: BCPE Oceandrive Buyer, Inc., Senior Secured First Lien Debt 4          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     33,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     0    
Gross additions     4,264,000    
Gross reductions     (133,000)    
Realized Gain/(Loss)     0    
Change in Unrealized Gain (Loss)     215,000    
Fair value, ending balance 4,346,000   4,346,000   0
Investment, Identifier [Axis]: Battalion CLO, Ltd. 21-17A F, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     570,000    
Fair value, ending balance 417,000   417,000   570,000
Investment, Identifier [Axis]: Bayou Holdings Buyer, Inc. | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (29,000)    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   (29,000) [8],[14]
Investment, Identifier [Axis]: Bayou Holdings Buyer, Inc. | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (31,000)    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   (31,000) [8],[14]
Investment, Identifier [Axis]: Bayou Holdings Buyer, Inc. | Professional Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     21,200,000    
Fair value, ending balance 21,196,000 [9],[10]   21,196,000 [9],[10]   21,200,000 [7],[8]
Investment, Identifier [Axis]: Beach Acquisition Bidco, LLC, Textiles, Apparel & luxury goods          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,460,000    
Fair value, ending balance 1,448,000   1,448,000   1,460,000
Investment, Identifier [Axis]: Bella Holding Co., LLC , Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 7,920,000   7,920,000    
Investment, Identifier [Axis]: Bella Holding Co., LLC, Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     8,047,000    
Fair value, ending balance         8,047,000
Investment, Identifier [Axis]: Belron Finance 2019, LLC, Diversified Consumer Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,756,000    
Fair value, ending balance 5,691,000   5,691,000   5,756,000
Investment, Identifier [Axis]: Big Apple Advisory, LLC | Financial Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     5,209,000    
Fair value, ending balance 6,092,000 [10],[13]   6,092,000 [10],[13]   5,209,000 [8],[14]
Investment, Identifier [Axis]: Big Apple Advisory, LLC | Financial Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Big Apple Advisory, LLC | Financial Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     47,166,000    
Fair value, ending balance 46,929,000 [9],[10],[12]   46,929,000 [9],[10],[12]   47,166,000 [7],[8],[11]
Investment, Identifier [Axis]: Bingo Group Buyer, Inc. | Commercial Services & Supplies 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 1,543,000 [10]   1,543,000 [10]   0 [8],[14]
Investment, Identifier [Axis]: Bingo Group Buyer, Inc. | Commercial Services & Supplies 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     1,551,000    
Fair value, ending balance 1,682,000 [10]   1,682,000 [10]   1,551,000 [8]
Investment, Identifier [Axis]: Bingo Group Buyer, Inc. | Commercial Services & Supplies 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     1,691,000    
Fair value, ending balance 644,000 [10],[13]   644,000 [10],[13]   1,691,000 [8]
Investment, Identifier [Axis]: Bingo Group Buyer, Inc. | Commercial Services & Supplies 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     20,000    
Fair value, ending balance [8],[14]         20,000
Investment, Identifier [Axis]: Bingo Group Buyer, Inc. | Commercial Services & Supplies 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     5,410,000    
Fair value, ending balance 5,382,000 [9],[10],[12]   5,382,000 [9],[10],[12]   5,410,000 [7],[8],[11]
Investment, Identifier [Axis]: Bingo Group Buyer, Inc.| Commercial Services & Supplies 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 20,000   20,000    
Investment, Identifier [Axis]: Black Mountain Sand, LLC | Energy Equipment & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[22]     1,304,000    
Fair value, ending balance 1,304,000 [10],[20],[23]   1,304,000 [10],[20],[23]   1,304,000 [8],[16],[17],[22]
Investment, Identifier [Axis]: Blackhawk Network Holdings, Inc., Professional Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,944,000    
Fair value, ending balance 4,873,000   4,873,000   4,944,000
Investment, Identifier [Axis]: Blackstone CQP Holdco, LP, Oil, Gas & Consumable Fuels          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,929,000    
Fair value, ending balance         4,929,000
Investment, Identifier [Axis]: Bond German BidCo 2 GmbH Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 1,690,000   1,690,000    
Investment, Identifier [Axis]: Bond US Bidco 1, Inc., Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 504,000   504,000    
Investment, Identifier [Axis]: CCI Buyer, Inc. | Wireless Telecommunication Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: CCI Buyer, Inc. | Wireless Telecommunication Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     52,129,000    
Fair value, ending balance 51,867,000 [9],[10],[12]   51,867,000 [9],[10],[12]   52,129,000 [7],[8],[11]
Investment, Identifier [Axis]: CD&R Hydra Buyer, Inc., Industrial Conglomerates          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,182,000    
Fair value, ending balance 8,150,000   8,150,000   6,182,000
Investment, Identifier [Axis]: CNT Holdings I Corp., Personal Care Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,043,000    
Fair value, ending balance 6,003,000   6,003,000   6,043,000
Investment, Identifier [Axis]: CQP Holdco, LP, Oil, Gas & Consumable Fuels          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 4,884,000   4,884,000    
Investment, Identifier [Axis]: CRS-SPV, Inc. | Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[24]     2,008,000    
Fair value, ending balance [8],[16],[17],[24]         2,008,000
Investment, Identifier [Axis]: CRS-SPV, Inc., Equity/Other Investments          
Schedule of Investments [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     2,008,000 1,704,000 1,704,000
Gross additions     0   0
Gross reductions     (2,068,000)   0
Realized Gain/(Loss)     507,000   0
Change in Unrealized Gain (Loss)     (447,000)   304,000
Fair value, ending balance 0   0   2,008,000
Investment, Identifier [Axis]: Calcasieu Pass Funding, LLC Energy Equipment & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 3,707,000   3,707,000    
Investment, Identifier [Axis]: Capstone Acquisition Holdings, Inc. | Air Freight & Logistics 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     208,000    
Fair value, ending balance 207,000 [10]   207,000 [10]   208,000 [8]
Investment, Identifier [Axis]: Capstone Acquisition Holdings, Inc. | Air Freight & Logistics 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     20,550,000    
Fair value, ending balance 20,446,000 [9],[10]   20,446,000 [9],[10]   20,550,000 [7],[8]
Investment, Identifier [Axis]: Capstone Acquisition Holdings, Inc. | Air Freight & Logistics 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 0   0    
Investment, Identifier [Axis]: Carlyle GMS CLO, 16-3A FRR, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,823,000    
Fair value, ending balance 1,731,000   1,731,000   1,823,000
Investment, Identifier [Axis]: Carr, Riggs & Ingram Capital, LLC | Financial Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     1,592,000    
Fair value, ending balance 2,090,000 [10],[13]   2,090,000 [10],[13]   1,592,000 [8],[14]
Investment, Identifier [Axis]: Carr, Riggs & Ingram Capital, LLC | Financial Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 441,000 [10],[13]   441,000 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Carr, Riggs & Ingram Capital, LLC | Financial Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     11,620,000    
Fair value, ending balance 11,562,000 [9],[10],[12]   11,562,000 [9],[10],[12]   11,620,000 [7],[8],[11]
Investment, Identifier [Axis]: Center Phase Energy, LLC | Electric Utilities 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     10,305,000    
Fair value, ending balance 2,386,000 [10],[20],[23]   2,386,000 [10],[20],[23]   10,305,000 [7],[8]
Investment, Identifier [Axis]: Center Phase Energy, LLC | Electric Utilities 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     15,186,000    
Fair value, ending balance 748,000 [10],[20],[23]   748,000 [10],[20],[23]   15,186,000 [7],[8]
Investment, Identifier [Axis]: Center Phase Energy, LLC | Electric Utilities 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[17],[22]     2,386,000    
Fair value, ending balance 10,305,000 [9],[10]   10,305,000 [9],[10]   2,386,000 [8],[17],[22]
Investment, Identifier [Axis]: Center Phase Energy, LLC | Electric Utilities 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[17],[22]     636,000    
Fair value, ending balance 15,109,000 [9],[10]   15,109,000 [9],[10]   636,000 [8],[17],[22]
Investment, Identifier [Axis]: Charter Communications Operating, LLC Media          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 644,000   644,000    
Investment, Identifier [Axis]: Charter Industries Holdings, LLC | Distributors 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (34,000)    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   (34,000) [8],[14]
Investment, Identifier [Axis]: Charter Industries Holdings, LLC | Distributors 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (51,000)    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   (51,000) [8],[14]
Investment, Identifier [Axis]: Charter Industries Holdings, LLC | Distributors 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     29,807,000    
Fair value, ending balance 29,255,000 [9],[10]   29,255,000 [9],[10]   29,807,000 [7],[8]
Investment, Identifier [Axis]: Cirque Du Soleil Holding USA Newco, Inc. | Entertainment          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [16],[17],[24],[25]     14,632,000    
Fair value, ending balance 18,849,000 [19],[20],[26]   18,849,000 [19],[20],[26]   14,632,000 [16],[17],[24],[25]
Investment, Identifier [Axis]: Cirque Du Soleil Holding USA Newco, Inc., Entertainment          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,756,000    
Fair value, ending balance 7,018,000   7,018,000   6,756,000
Investment, Identifier [Axis]: Cirque Du Soleil Holding USA Newco, Inc., Equity/Other Investments          
Schedule of Investments [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     14,632,000 0 0
Gross additions     0   17,441,000
Gross reductions     (14,632,000)   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     0   (2,809,000)
Fair value, ending balance 0   0   14,632,000
Investment, Identifier [Axis]: Citadel Securities Global Holdings, LLC Financial Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 4,389,000   4,389,000    
Investment, Identifier [Axis]: Citadel Securities, LP, Financial Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,432,000    
Fair value, ending balance         4,432,000
Investment, Identifier [Axis]: Clarios Global, LP, Automobile Components          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     10,012,000    
Fair value, ending balance 9,950,000   9,950,000   10,012,000
Investment, Identifier [Axis]: Cliffwater, LLC | Capital Markets 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 0   0    
Investment, Identifier [Axis]: Cliffwater, LLC | Capital Markets 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 30,002,000   30,002,000    
Investment, Identifier [Axis]: Cliffwater, LLC | Financial Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance [8],[14]         0
Investment, Identifier [Axis]: Cliffwater, LLC | Financial Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     30,154,000    
Fair value, ending balance [7],[8],[11]         30,154,000
Investment, Identifier [Axis]: Clover Holding 2, LLC, Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,219,000    
Fair value, ending balance 4,955,000   4,955,000   5,219,000
Investment, Identifier [Axis]: Clydesdale Acquisition Holdings, Inc. Containers & Packaging          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 3,829,000   3,829,000    
Investment, Identifier [Axis]: Coalesce Merlin Purchaser, LLC | Commercial Services & Supplies 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     715,000    
Fair value, ending balance 5,699,000 [10],[13]   5,699,000 [10],[13]   715,000 [8],[14]
Investment, Identifier [Axis]: Coalesce Merlin Purchaser, LLC | Commercial Services & Supplies 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (32,000)    
Fair value, ending balance 300,000 [10],[13]   300,000 [10],[13]   (32,000) [8],[14]
Investment, Identifier [Axis]: Coalesce Merlin Purchaser, LLC | Commercial Services & Supplies 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     17,300,000    
Fair value, ending balance 17,213,000 [9],[10],[12]   17,213,000 [9],[10],[12]   17,300,000 [7],[8],[11]
Investment, Identifier [Axis]: Cold Spring Brewing, Co. | Beverages          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     20,556,000    
Fair value, ending balance 20,180,000 [9],[10],[12]   20,180,000 [9],[10],[12]   20,556,000 [7],[8],[11]
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC ) | Professional Services 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 2,408,000   2,408,000    
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     1,188,000    
Fair value, ending balance 739,000 [10],[13]   739,000 [10],[13]   1,188,000 [8],[14]
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     24,672,000    
Fair value, ending balance 24,543,000 [9],[10]   24,543,000 [9],[10]   24,672,000 [7],[8]
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC | Professional Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     24,357,000    
Fair value, ending balance 24,234,000 [9],[10]   24,234,000 [9],[10]   24,357,000 [7],[8]
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC | Professional Services 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     2,420,000    
Fair value, ending balance [7],[8]         2,420,000
Investment, Identifier [Axis]: Communication Technology Intermediate, LLC | Professional Services 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     8,582,000    
Fair value, ending balance 8,537,000 [9],[10],[12]   8,537,000 [9],[10],[12]   8,582,000 [7],[8],[11]
Investment, Identifier [Axis]: Compass Power Generation, LLC, Independent Power and Renewable Electricity Producers          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,467,000    
Fair value, ending balance 6,178,000   6,178,000   6,467,000
Investment, Identifier [Axis]: Connectwise, LL, Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 5,138,000   5,138,000    
Investment, Identifier [Axis]: Connectwise, LLC, Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     10,427,000    
Fair value, ending balance         10,427,000
Investment, Identifier [Axis]: Conservice Midco, LLC, Diversified Consumer Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,423,000    
Fair value, ending balance         5,423,000
Investment, Identifier [Axis]: Consolidated Precision Products Corp. | Aerospace & Defense          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[22]     21,867,000    
Fair value, ending balance 19,728,000 [10],[23]   19,728,000 [10],[23]   21,867,000 [8],[22]
Investment, Identifier [Axis]: Corelogic, Inc. | Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9] 9,110,000   9,110,000    
Investment, Identifier [Axis]: Corelogic, Inc. | IT Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7]     9,326,000    
Fair value, ending balance [7]         9,326,000
Investment, Identifier [Axis]: Corelogic, Inc., Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 8,725,000   8,725,000    
Investment, Identifier [Axis]: Corelogic, Inc., IT Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     8,879,000    
Fair value, ending balance         8,879,000
Investment, Identifier [Axis]: Coreweave Financing DDTL V, LLC IT Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 506,000   506,000    
Investment, Identifier [Axis]: Corfin Industries, LLC | Aerospace & Defense 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 1,545,000   1,545,000    
Investment, Identifier [Axis]: Corfin Industries, LLC | Aerospace & Defense 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 9,411,000   9,411,000    
Investment, Identifier [Axis]: Corfin Industries, LLC | Aerospace & Defense 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 15,807,000   15,807,000    
Investment, Identifier [Axis]: Corfin Industries, LLC | Aerospace & Defense 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 19,533,000   19,533,000    
Investment, Identifier [Axis]: Corfin Industries, LLC | Electrical Equipment 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     1,549,000    
Fair value, ending balance [8]         1,549,000
Investment, Identifier [Axis]: Corfin Industries, LLC | Electrical Equipment 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     9,435,000    
Fair value, ending balance [8]         9,435,000
Investment, Identifier [Axis]: Corfin Industries, LLC | Electrical Equipment 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     15,849,000    
Fair value, ending balance [7],[8],[11]         15,849,000
Investment, Identifier [Axis]: Corfin Industries, LLC | Electrical Equipment 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     19,582,000    
Fair value, ending balance [7],[8],[11]         19,582,000
Investment, Identifier [Axis]: Cornerstone Building Brands, Inc., Building Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,798,000    
Fair value, ending balance         2,798,000
Investment, Identifier [Axis]: Cornerstone Chemical, Co. | Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     3,107,000    
Fair value, ending balance 0 [10],[19],[20]   0 [10],[19],[20]   3,107,000 [8],[16],[17]
Investment, Identifier [Axis]: Coronis Health I, LLC | Health Care Technology          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[27] 2,820,000   2,820,000    
Investment, Identifier [Axis]: Coronis Health I, LLC | Health Care Technology 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14],[24]     532,000    
Fair value, ending balance 798,000 [10],[13],[27]   798,000 [10],[13],[27]   532,000 [8],[14],[24]
Investment, Identifier [Axis]: Coronis Health I, LLC | Health Care Technology 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[24]     4,225,000    
Fair value, ending balance 4,458,000 [10],[27]   4,458,000 [10],[27]   4,225,000 [8],[24]
Investment, Identifier [Axis]: Coronis Health I, LLC | Health Care Technology 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[24]     2,751,000    
Fair value, ending balance 4,900,000 [10],[19],[20],[27]   4,900,000 [10],[19],[20],[27]   2,751,000 [8],[24]
Investment, Identifier [Axis]: Coronis Health I, LLC | Health Care Technology 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[24]     4,900,000    
Fair value, ending balance [8],[16],[17],[24]         4,900,000
Investment, Identifier [Axis]: Coronis Health I, LLC, Equity/Other Investments          
Schedule of Investments [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     4,900,000 0 0
Gross additions     0   4,900,000
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     0   0
Fair value, ending balance 4,900,000   4,900,000   4,900,000
Investment, Identifier [Axis]: Coronis Health I, LLC, Senior Secured First Lien Debt 1          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     32,000   37,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     532,000 0 0
Gross additions     266,000   532,000
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     0   0
Fair value, ending balance 798,000   798,000   532,000
Investment, Identifier [Axis]: Coronis Health I, LLC, Senior Secured First Lien Debt 2          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     234,000   311,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,225,000 0 0
Gross additions     233,000   4,225,000
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     0   0
Fair value, ending balance 4,458,000   4,458,000   4,225,000
Investment, Identifier [Axis]: Coronis Health I, LLC, Senior Secured Second Lien Debt          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     70,000   92,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,751,000 0 0
Gross additions     69,000   2,751,000
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     0   0
Fair value, ending balance 2,820,000   2,820,000   2,751,000
Investment, Identifier [Axis]: Cotiviti, Inc., Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,528,000    
Fair value, ending balance 4,262,000   4,262,000   4,528,000
Investment, Identifier [Axis]: Cotiviti, Inc., Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     9,424,000    
Fair value, ending balance 8,927,000   8,927,000   9,424,000
Investment, Identifier [Axis]: Crisis Prevention Institute, Inc., Diversified Consumer Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,290,000    
Fair value, ending balance 2,267,000   2,267,000   2,290,000
Investment, Identifier [Axis]: Crown Finance US, Inc., Entertainment          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,873,000    
Fair value, ending balance 4,931,000   4,931,000   4,873,000
Investment, Identifier [Axis]: Danish CRJ, Ltd. (2) (4), Equity/Other Investments          
Schedule of Investments [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]: DayMark Wealth Partners, LLC | Financial Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (40,000)   (40,000)    
Investment, Identifier [Axis]: DayMark Wealth Partners, LLC | Financial Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (5,000)   (5,000)    
Investment, Identifier [Axis]: DayMark Wealth Partners, LLC | Financial Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 2,970,000   2,970,000    
Investment, Identifier [Axis]: Demakes Borrower, LLC | Consumer Staples Distribution & Retail          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     17,577,000    
Fair value, ending balance 17,466,000 [9],[10]   17,466,000 [9],[10]   17,577,000 [7],[8]
Investment, Identifier [Axis]: Directv Financing, LLC, Media          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     196,000    
Fair value, ending balance         196,000
Investment, Identifier [Axis]: EIG Management Co., LLC, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,442,000    
Fair value, ending balance 3,442,000   3,442,000   3,442,000
Investment, Identifier [Axis]: EMRLD Borrower, LP, Machinery          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 1,859,000   1,859,000    
Investment, Identifier [Axis]: Eaton Vance CDO, Ltd. 15-1A FR, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     846,000    
Fair value, ending balance 227,000   227,000   846,000
Investment, Identifier [Axis]: Edelman Financial Center, LLC | Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7]     9,468,000    
Fair value, ending balance [7]         9,468,000
Investment, Identifier [Axis]: Edelman Financial Center, LLC, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,734,000    
Fair value, ending balance         4,734,000
Investment, Identifier [Axis]: Edelman Financial Engines Center, LLC Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 4,760,000   4,760,000    
Investment, Identifier [Axis]: Einstein Parent, Inc. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (12,000)    
Fair value, ending balance (69,000) [10],[13]   (69,000) [10],[13]   (12,000) [8],[14]
Investment, Identifier [Axis]: Einstein Parent, Inc. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     22,206,000    
Fair value, ending balance 21,648,000 [9],[10],[12]   21,648,000 [9],[10],[12]   22,206,000 [7],[8],[11]
Investment, Identifier [Axis]: Electric Power Engineers, LLC | Construction & Engineering 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 6,379,000   6,379,000    
Investment, Identifier [Axis]: Electric Power Engineers, LLC | Construction & Engineering 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 2,127,000   2,127,000    
Investment, Identifier [Axis]: Electric Power Engineers, LLC | Construction & Engineering 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 27,909,000   27,909,000    
Investment, Identifier [Axis]: Electric Power Engineers, LLC | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance [8],[14]         0
Investment, Identifier [Axis]: Electric Power Engineers, LLC | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance [8],[14]         0
Investment, Identifier [Axis]: Electric Power Engineers, LLC | Professional Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     27,909,000    
Fair value, ending balance [7],[8],[11]         27,909,000
Investment, Identifier [Axis]: Electro-Methods, LP | Aerospace & Defense 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 0   0    
Investment, Identifier [Axis]: Electro-Methods, LP | Aerospace & Defense 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 34,239,000   34,239,000    
Investment, Identifier [Axis]: Electro-Methods, LP | Machinery 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance [8],[14]         0
Investment, Identifier [Axis]: Electro-Methods, LP | Machinery 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     34,412,000    
Fair value, ending balance [7],[8],[11]         34,412,000
Investment, Identifier [Axis]: Eliassen Group, LLC | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     1,344,000    
Fair value, ending balance 1,299,000 [9],[10]   1,299,000 [9],[10]   1,344,000 [7],[8]
Investment, Identifier [Axis]: Eliassen Group, LLC | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     16,802,000    
Fair value, ending balance 16,247,000 [9],[10],[12]   16,247,000 [9],[10],[12]   16,802,000 [7],[8],[11]
Investment, Identifier [Axis]: Emerald Borrower, LP Machinery          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,279,000   2,279,000    
Investment, Identifier [Axis]: Emerald Borrower, LP, Machinery          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,297,000    
Fair value, ending balance         2,297,000
Investment, Identifier [Axis]: Emma Buyer, LLC Media 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance (1,000)   (1,000)    
Investment, Identifier [Axis]: Emma Buyer, LLC Media 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance (1,000)   (1,000)    
Investment, Identifier [Axis]: Emma Buyer, LLC Media 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 1,302,000   1,302,000    
Investment, Identifier [Axis]: Ensemble RCM, LLC, Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     13,368,000    
Fair value, ending balance 12,945,000   12,945,000   13,368,000
Investment, Identifier [Axis]: Entain, PLC, Hotels, Restaurants & Leisure 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,747,000    
Fair value, ending balance 4,756,000   4,756,000   4,747,000
Investment, Identifier [Axis]: Entain, PLC, Hotels, Restaurants & Leisure 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,435,000    
Fair value, ending balance 3,435,000   3,435,000   3,435,000
Investment, Identifier [Axis]: Epicor Software Corp., Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,086,000    
Fair value, ending balance 5,760,000   5,760,000   6,086,000
Investment, Identifier [Axis]: FBLC Senior Loan Fund, LLC | Investment in Joint Ventures          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[17],[18],[28]     224,956,000    
Fair value, ending balance 218,207,000 [10],[20],[21],[26],[29]   218,207,000 [10],[20],[21],[26],[29]   224,956,000 [8],[17],[18],[28]
Investment, Identifier [Axis]: FBLC Senior Loan Fund, LLC, Joint Venture          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     10,040,000   27,380,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     224,956,000 404,934,000 404,934,000
Gross additions     0   0
Gross reductions     0   (179,978,000)
Realized Gain/(Loss)     0   (296,000)
Change in Unrealized Gain (Loss)     (6,749,000)   296,000
Fair value, ending balance 218,207,000   218,207,000   224,956,000
Investment, Identifier [Axis]: FGT Purchaser, LLC | Specialty Retail 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (296,000)    
Fair value, ending balance (296,000) [10],[13]   (296,000) [10],[13]   (296,000) [8],[14]
Investment, Identifier [Axis]: FGT Purchaser, LLC | Specialty Retail 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     28,164,000    
Fair value, ending balance 28,449,000 [9],[10]   28,449,000 [9],[10]   28,164,000 [7],[8]
Investment, Identifier [Axis]: FNZ Group Entities, Ltd., Financial Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,330,000    
Fair value, ending balance 2,327,000   2,327,000   2,330,000
Investment, Identifier [Axis]: Faraday Buyer, LLC | Electrical Equipment 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     40,805,000    
Fair value, ending balance [7],[8]         40,805,000
Investment, Identifier [Axis]: Faraday Buyer, LLC | Electrical Equipment 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     8,644,000    
Fair value, ending balance [7],[8]         8,644,000
Investment, Identifier [Axis]: Fiesta Purchaser, Inc. Food Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 3,909,000   3,909,000    
Investment, Identifier [Axis]: FinThrive Software Intermediate Holdings, Inc., Health Care Technology          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,732,000    
Fair value, ending balance 1,452,000   1,452,000   2,732,000
Investment, Identifier [Axis]: First Eagle Greenway Fund II, LLC, Equity/Other Investments          
Schedule of Investments [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     0 255,000 255,000
Gross additions         0
Gross reductions         (244,000)
Realized Gain/(Loss)         (131,000)
Change in Unrealized Gain (Loss)         120,000
Fair value, ending balance         0
Investment, Identifier [Axis]: Fitness International, LLC, Hotels, Restaurants & Leisure          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,839,000    
Fair value, ending balance 6,791,000   6,791,000   6,839,000
Investment, Identifier [Axis]: FloWorks International, LLC | Machinery 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     4,958,000    
Fair value, ending balance [8]         4,958,000
Investment, Identifier [Axis]: FloWorks International, LLC | Machinery 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     39,366,000    
Fair value, ending balance [7],[8],[11]         39,366,000
Investment, Identifier [Axis]: FloWorks International, LLC | Trading Companies & Distributors 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 4,945,000   4,945,000    
Investment, Identifier [Axis]: FloWorks International, LLC | Trading Companies & Distributors 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 39,167,000   39,167,000    
Investment, Identifier [Axis]: Florida Food Products, LLC | Food Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 7,457,000   7,457,000    
Investment, Identifier [Axis]: Florida Food Products, LLC | Food Products 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7]     7,555,000    
Fair value, ending balance [7]         7,555,000
Investment, Identifier [Axis]: Florida Food Products, LLC | Food Products 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     1,916,000    
Fair value, ending balance [7],[8]         1,916,000
Investment, Identifier [Axis]: Florida Food Products, LLC | Food Products 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7]     1,890,000    
Fair value, ending balance [7]         1,890,000
Investment, Identifier [Axis]: Flow Traders Holding, LLC | Capital Markets 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14],[25]     (91,000)    
Fair value, ending balance 16,328,000 [10],[26]   16,328,000 [10],[26]   (91,000) [8],[14],[25]
Investment, Identifier [Axis]: Flow Traders Holding, LLC | Capital Markets 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[25]     16,389,000    
Fair value, ending balance 2,835,000 [10],[13],[26]   2,835,000 [10],[13],[26]   16,389,000 [8],[25]
Investment, Identifier [Axis]: Focus Financial Partners, LLC, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,443,000    
Fair value, ending balance 4,302,000   4,302,000   4,443,000
Investment, Identifier [Axis]: Foresight Energy Operating, LL, Oil, Gas & Consumable Fuels          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 644,000   644,000    
Investment, Identifier [Axis]: Foresight Energy Operating, LLC | Oil, Gas & Consumable Fuels          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 1,031,000   1,031,000    
Investment, Identifier [Axis]: Foresight Energy Operating, LLC | Oil, Gas & Consumable Fuels 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     1,037,000    
Fair value, ending balance 876,000 [10],[19],[20],[23]   876,000 [10],[19],[20],[23]   1,037,000 [8]
Investment, Identifier [Axis]: Foresight Energy Operating, LLC | Oil, Gas & Consumable Fuels 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[22]     876,000    
Fair value, ending balance [8],[16],[17],[22]         876,000
Investment, Identifier [Axis]: Foresight Energy Operating, LLC, Oil, Gas & Consumable Fuels          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     648,000    
Fair value, ending balance         648,000
Investment, Identifier [Axis]: Freeport LNG Investments, LLLP, Oil, Gas & Consumable Fuels          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,820,000    
Fair value, ending balance 5,004,000   5,004,000   4,820,000
Investment, Identifier [Axis]: GRVTY, Inc. | Aerospace & Defense 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[12] 3,290,000   3,290,000    
Investment, Identifier [Axis]: GRVTY, Inc. | Aerospace & Defense 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (23,000)   (23,000)    
Investment, Identifier [Axis]: GRVTY, Inc. | Aerospace & Defense 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (12,000)   (12,000)    
Investment, Identifier [Axis]: Gainwell Acquisition Corp., Health Care Technology          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,937,000   2,937,000    
Investment, Identifier [Axis]: Galaxy US OpCo, Inc., Professional Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,229,000    
Fair value, ending balance         2,229,000
Investment, Identifier [Axis]: Galway Borrower, LLC | Insurance 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     920,000    
Fair value, ending balance 1,122,000 [10]   1,122,000 [10]   920,000 [8],[14]
Investment, Identifier [Axis]: Galway Borrower, LLC | Insurance 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     581,000    
Fair value, ending balance 1,055,000 [10],[13]   1,055,000 [10],[13]   581,000 [8],[14]
Investment, Identifier [Axis]: Galway Borrower, LLC | Insurance 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     38,101,000    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   38,101,000 [7],[8]
Investment, Identifier [Axis]: Galway Borrower, LLC | Insurance 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 37,911,000   37,911,000    
Investment, Identifier [Axis]: Geon Performance Solutions, LLC, Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,555,000    
Fair value, ending balance 4,217,000   4,217,000   3,555,000
Investment, Identifier [Axis]: Geosyntec Consultants, Inc., Professional Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     9,227,000    
Fair value, ending balance 9,120,000   9,120,000   9,227,000
Investment, Identifier [Axis]: Global Medical Response, Inc., Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     10,022,000    
Fair value, ending balance 8,079,000   8,079,000   10,022,000
Investment, Identifier [Axis]: GoHealth, Inc. | Insurance          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [16],[22]     7,000    
Fair value, ending balance 1,000 [19],[23]   1,000 [19],[23]   7,000 [16],[22]
Investment, Identifier [Axis]: Golden State Foods, LLC, Food Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,450,000    
Fair value, ending balance 6,406,000   6,406,000   6,450,000
Investment, Identifier [Axis]: Gordian Medical, Inc. | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     0    
Fair value, ending balance 0 [10],[19],[20]   0 [10],[19],[20]   0 [8],[16],[17]
Investment, Identifier [Axis]: Gordian Medical, Inc. | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[17]     2,944,000    
Fair value, ending balance 2,944,000 [9],[10],[19],[20]   2,944,000 [9],[10],[19],[20]   2,944,000 [7],[8],[17]
Investment, Identifier [Axis]: Gordian Medical, Inc., Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 7,316,000   7,316,000    
Investment, Identifier [Axis]: Gordian Medical, Inc., Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,316,000    
Fair value, ending balance 0   0   7,316,000
Investment, Identifier [Axis]: Gordian Medical, Inc., Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     0    
Fair value, ending balance         0
Investment, Identifier [Axis]: Graftech Global Enterprises, Inc. Electrical Equipment 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 1,042,000   1,042,000    
Investment, Identifier [Axis]: Graftech Global Enterprises, Inc. Electrical Equipment 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 1,824,000   1,824,000    
Investment, Identifier [Axis]: Greywolf CLO, Ltd. 20-3RA ER, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     916,000    
Fair value, ending balance 729,000   729,000   916,000
Investment, Identifier [Axis]: Groome Purchaser, LLC | Commercial Services & Supplies 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (33,000)    
Fair value, ending balance 3,479,000 [10]   3,479,000 [10]   (33,000) [8],[14]
Investment, Identifier [Axis]: Groome Purchaser, LLC | Commercial Services & Supplies 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (49,000)    
Fair value, ending balance 832,000 [10],[13]   832,000 [10],[13]   (49,000) [8],[14]
Investment, Identifier [Axis]: Groome Purchaser, LLC | Commercial Services & Supplies 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (25,000)    
Fair value, ending balance (23,000) [10],[13]   (23,000) [10],[13]   (25,000) [8],[14]
Investment, Identifier [Axis]: Groome Purchaser, LLC | Commercial Services & Supplies 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     16,368,000    
Fair value, ending balance 16,299,000 [9],[10]   16,299,000 [9],[10]   16,368,000 [7],[8]
Investment, Identifier [Axis]: Gulfside Supply, Inc., Building Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,375,000    
Fair value, ending balance 3,699,000   3,699,000   4,375,000
Investment, Identifier [Axis]: Hamilton Projects Acquiror, LLC, Independent Power and Renewable Electricity Producers          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,617,000    
Fair value, ending balance         6,617,000
Investment, Identifier [Axis]: HelpSystems Holdings, Inc., Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,139,000    
Fair value, ending balance 4,937,000   4,937,000   4,139,000
Investment, Identifier [Axis]: Higginbotham Insurance Agency, Inc. | Insurance          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[17]     10,046,000    
Fair value, ending balance 10,046,000 [10],[20]   10,046,000 [10],[20]   10,046,000 [8],[17]
Investment, Identifier [Axis]: High Street Buyer, Inc. | Insurance          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     3,259,000    
Fair value, ending balance 5,035,000 [10],[13]   5,035,000 [10],[13]   3,259,000 [8],[14]
Investment, Identifier [Axis]: Highbridge Loan Management, Ltd. 11A-17 E, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,592,000    
Fair value, ending balance 2,201,000   2,201,000   2,592,000
Investment, Identifier [Axis]: Hologic, Inc. | Health Care Equipment & Supplies          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 6,964,000   6,964,000    
Investment, Identifier [Axis]: Hologic, Inc., Health Care Equipment & Supplies          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 9,777,000   9,777,000    
Investment, Identifier [Axis]: Hometown Food, Co. | Food Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     14,973,000    
Fair value, ending balance 14,921,000 [9],[10],[12]   14,921,000 [9],[10],[12]   14,973,000 [7],[8],[11]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc. | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     4,615,000    
Fair value, ending balance 4,592,000 [10]   4,592,000 [10]   4,615,000 [8]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc. | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     2,085,000    
Fair value, ending balance 2,122,000 [10]   2,122,000 [10]   2,085,000 [8],[14]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc. | Health Care Providers & Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     2,132,000    
Fair value, ending balance 2,204,000 [10],[13]   2,204,000 [10],[13]   2,132,000 [8]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc. | Health Care Providers & Services 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     24,828,000    
Fair value, ending balance 24,705,000 [9],[10]   24,705,000 [9],[10]   24,828,000 [7],[8]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc. | Health Care Providers & Services 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     6,444,000    
Fair value, ending balance 6,412,000 [9],[10]   6,412,000 [9],[10]   6,444,000 [7],[8]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc. | Health Care Providers & Services 6          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     8,401,000    
Fair value, ending balance 8,359,000 [9],[10]   8,359,000 [9],[10]   8,401,000 [7],[8]
Investment, Identifier [Axis]: Hospice Care Buyer, Inc. | Health Care Providers & Services 7          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     3,528,000    
Fair value, ending balance 3,510,000 [9],[10]   3,510,000 [9],[10]   3,528,000 [7],[8]
Investment, Identifier [Axis]: Hudson River Trading, LLC, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,243,000    
Fair value, ending balance 5,158,000   5,158,000   5,243,000
Investment, Identifier [Axis]: Hunter Communications & Technologies, LLC | Diversified Telecommunication Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 410,000   410,000    
Investment, Identifier [Axis]: Hunter Communications & Technologies, LLC | Diversified Telecommunication Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (6,000)   (6,000)    
Investment, Identifier [Axis]: Hunter Communications & Technologies, LLC | Diversified Telecommunication Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 5,756,000   5,756,000    
Investment, Identifier [Axis]: Hunter Douglas, Inc., Household Durables          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,500,000    
Fair value, ending balance 4,452,000   4,452,000   4,500,000
Investment, Identifier [Axis]: Hyperion Refinance SARL Insurance          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 3,754,000   3,754,000    
Investment, Identifier [Axis]: ICAT Intermediate Holdings, LLC | Air Freight & Logistics 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 4,658,000   4,658,000    
Investment, Identifier [Axis]: ICAT Intermediate Holdings, LLC | Air Freight & Logistics 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (15,000)   (15,000)    
Investment, Identifier [Axis]: ICAT Intermediate Holdings, LLC | Air Freight & Logistics 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (57,000)   (57,000)    
Investment, Identifier [Axis]: ICAT Intermediate Holdings, LLC | Air Freight & Logistics 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 17,018,000   17,018,000    
Investment, Identifier [Axis]: ICAT Intermediate Holdings, LLC | Ground Transportation 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     2,050,000    
Fair value, ending balance [8],[14]         2,050,000
Investment, Identifier [Axis]: ICAT Intermediate Holdings, LLC | Ground Transportation 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (18,000)    
Fair value, ending balance [8],[14]         (18,000)
Investment, Identifier [Axis]: ICAT Intermediate Holdings, LLC | Ground Transportation 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     17,066,000    
Fair value, ending balance [7],[8]         17,066,000
Investment, Identifier [Axis]: ICR Operations, LLC | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     3,784,000    
Fair value, ending balance [8],[14]         3,784,000
Investment, Identifier [Axis]: ICR Operations, LLC | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     40,839,000    
Fair value, ending balance [7],[8]         40,839,000
Investment, Identifier [Axis]: ICR Operations, LLC | Professional Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     2,219,000    
Fair value, ending balance [7],[8]         2,219,000
Investment, Identifier [Axis]: IDERA, Inc., Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 3,797,000   3,797,000    
Investment, Identifier [Axis]: IDERA, Inc., Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,602,000    
Fair value, ending balance         4,602,000
Investment, Identifier [Axis]: IDERA, Inc., Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     933,000    
Fair value, ending balance 622,000   622,000   933,000
Investment, Identifier [Axis]: IG Investments Holdings, LLC | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: IG Investments Holdings, LLC | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     26,001,000    
Fair value, ending balance 25,869,000 [9],[10]   25,869,000 [9],[10]   26,001,000 [7],[8]
Investment, Identifier [Axis]: ION Platform Finance US, Inc., Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,803,000    
Fair value, ending balance 3,283,000   3,283,000   3,803,000
Investment, Identifier [Axis]: IQN Holding Corp. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     5,790,000    
Fair value, ending balance 5,778,000 [10]   5,778,000 [10]   5,790,000 [8]
Investment, Identifier [Axis]: IQN Holding Corp. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     988,000    
Fair value, ending balance 889,000 [10],[13]   889,000 [10],[13]   988,000 [8],[14]
Investment, Identifier [Axis]: IQN Holding Corp. | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     17,329,000    
Fair value, ending balance 17,205,000 [9],[10],[12]   17,205,000 [9],[10],[12]   17,329,000 [7],[8],[11]
Investment, Identifier [Axis]: IXS Holdings, Inc. Automobiles          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,964,000   2,964,000    
Investment, Identifier [Axis]: Icon Parent I, Inc., Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,981,000    
Fair value, ending balance 4,621,000   4,621,000   4,981,000
Investment, Identifier [Axis]: Ideal Tridon Holdings, Inc. | Machinery          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (67,000)   (67,000)    
Investment, Identifier [Axis]: Ideal Tridon Holdings, Inc. | Machinery 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (72,000)    
Fair value, ending balance [8],[14]         (72,000)
Investment, Identifier [Axis]: Ideal Tridon Holdings, Inc. | Machinery 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     804,000    
Fair value, ending balance 2,452,000 [10],[13]   2,452,000 [10],[13]   804,000 [8],[14]
Investment, Identifier [Axis]: Ideal Tridon Holdings, Inc. | Machinery 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     41,876,000    
Fair value, ending balance 41,695,000 [9],[10],[12]   41,695,000 [9],[10],[12]   41,876,000 [7],[8],[11]
Investment, Identifier [Axis]: Indigo Buyer, Inc. | Containers & Packaging 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     4,007,000    
Fair value, ending balance 9,764,000 [10],[13]   9,764,000 [10],[13]   4,007,000 [8],[14]
Investment, Identifier [Axis]: Indigo Buyer, Inc. | Containers & Packaging 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Indigo Buyer, Inc. | Containers & Packaging 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     60,879,000    
Fair value, ending balance 60,572,000 [9],[10]   60,572,000 [9],[10]   60,879,000 [7],[8]
Investment, Identifier [Axis]: InhabitIQ, Inc. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (31,000)    
Fair value, ending balance (109,000) [10],[13]   (109,000) [10],[13]   (31,000) [8],[14]
Investment, Identifier [Axis]: InhabitIQ, Inc. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (20,000)    
Fair value, ending balance (68,000) [10],[13]   (68,000) [10],[13]   (20,000) [8],[14]
Investment, Identifier [Axis]: InhabitIQ, Inc. | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     25,897,000    
Fair value, ending balance 25,490,000 [9],[10],[12]   25,490,000 [9],[10],[12]   25,897,000 [7],[8],[11]
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc, Equity/Other Investments 1          
Schedule of Investments [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]: Integrated Efficiency Solutions, Inc. | Electrical Equipment          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[19],[20],[23],[27] 0   0    
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc. | Electrical Equipment 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[24]     1,378,000    
Fair value, ending balance [8],[24]         1,378,000
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc. | Electrical Equipment 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[24],[30]     668,000    
Fair value, ending balance [8],[24],[30]         668,000
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc. | Electrical Equipment 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[22]     0    
Fair value, ending balance [8],[16],[17],[22]         0
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc. | Electrical Equipment 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[22]     0    
Fair value, ending balance [8],[16],[17],[22]         0
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Equity/Other Investments          
Schedule of Investments [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   0
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Equity/Other Investments 2          
Schedule of Investments [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]: Integrated Efficiency Solutions, Inc., Senior Secured First Lien Debt          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     8,000    
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,378,000    
Gross additions     0    
Gross reductions     (1,397,000)    
Realized Gain/(Loss)     18,000    
Change in Unrealized Gain (Loss)     1,000    
Fair value, ending balance 0   0   1,378,000
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Senior Secured First Lien Debt 1          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income         105,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,378,000 1,393,000 1,393,000
Gross additions         0
Gross reductions         (15,000)
Realized Gain/(Loss)         0
Change in Unrealized Gain (Loss)         0
Fair value, ending balance         1,378,000
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Senior Secured First Lien Debt 2          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income         10,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     0 210,000 210,000
Gross additions         150,000
Gross reductions         (360,000)
Realized Gain/(Loss)         0
Change in Unrealized Gain (Loss)         0
Fair value, ending balance         0
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Senior Secured First Lien Debt 3          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income         17,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     0 0 0
Gross additions         240,000
Gross reductions         (249,000)
Realized Gain/(Loss)         9,000
Change in Unrealized Gain (Loss)         0
Fair value, ending balance         0
Investment, Identifier [Axis]: Integrated Efficiency Solutions, Inc., Senior Secured Second Lien Debt          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     0   1,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     668,000 446,000 446,000
Gross additions     0   0
Gross reductions     (629,000)   0
Realized Gain/(Loss)     (446,000)   0
Change in Unrealized Gain (Loss)     407,000   222,000
Fair value, ending balance 0   0   668,000
Investment, Identifier [Axis]: Integrated Global Services, Inc. | Commercial Services & Supplies 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (72,000)    
Fair value, ending balance [8],[14]         (72,000)
Investment, Identifier [Axis]: Integrated Global Services, Inc. | Commercial Services & Supplies 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     1,560,000    
Fair value, ending balance [8],[14]         1,560,000
Investment, Identifier [Axis]: Integrated Global Services, Inc. | Commercial Services & Supplies 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     32,151,000    
Fair value, ending balance [7],[8],[11]         32,151,000
Investment, Identifier [Axis]: Integrated Global Services, Inc. | Construction & Engineering 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 0   0    
Investment, Identifier [Axis]: Integrated Global Services, Inc. | Construction & Engineering 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 5,060,000   5,060,000    
Investment, Identifier [Axis]: Integrated Global Services, Inc. | Construction & Engineering 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 32,417,000   32,417,000    
Investment, Identifier [Axis]: International Cruise & Excursion Gallery, Inc. | Hotels, Restaurants & Leisure          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[12],[19],[20] 0   0    
Investment, Identifier [Axis]: International Cruise & Excursion Gallery, Inc. | Hotels, Restaurants & Leisure 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[12] 1,358,000   1,358,000    
Investment, Identifier [Axis]: International Cruise & Excursion Gallery, Inc. | Hotels, Restaurants & Leisure 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[11],[16],[17],[22]     0    
Fair value, ending balance [8],[11],[16],[17],[22]         0
Investment, Identifier [Axis]: International Cruise & Excursion Gallery, Inc. | Hotels, Restaurants & Leisure A          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[11]     1,358,000    
Fair value, ending balance [8],[11]         1,358,000
Investment, Identifier [Axis]: Invenergy Thermal Operating I, LLC, Independent Power and Renewable Electricity Producers          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,578,000    
Fair value, ending balance         3,578,000
Investment, Identifier [Axis]: Invenergy Thermal Operating I, LLC, Independent Power and Renewable Electricity Producers 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 3,411,000   3,411,000    
Investment, Identifier [Axis]: Invenergy Thermal Operating I, LLC, Independent Power and Renewable Electricity Producers 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     226,000    
Fair value, ending balance 225,000   225,000   226,000
Investment, Identifier [Axis]: Jane Street Group, LLC, Financial Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     8,040,000    
Fair value, ending balance 7,962,000   7,962,000   8,040,000
Investment, Identifier [Axis]: Jump Financial, LLC, Financial Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,124,000    
Fair value, ending balance 7,186,000   7,186,000   7,124,000
Investment, Identifier [Axis]: KKR Financial CLO, Ltd. 15 FR, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,795,000    
Fair value, ending balance 697,000   697,000   1,795,000
Investment, Identifier [Axis]: Kahala Aviation, LLC | Asset Based Financing          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[18]     33,911,000    
Fair value, ending balance 58,990,000 [10],[21]   58,990,000 [10],[21]   33,911,000 [8],[18]
Investment, Identifier [Axis]: Kahala Aviation, LLC | Asset Based Financing 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[18]     10,330,000    
Fair value, ending balance 16,125,000 [10],[19],[20],[21]   16,125,000 [10],[19],[20],[21]   10,330,000 [8],[16],[17],[18]
Investment, Identifier [Axis]: Kahala Aviation, LLC, Equity/Other Investments          
Schedule of Investments [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     10,330,000 2,308,000 2,308,000
Gross additions     5,468,000   7,545,000
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     327,000   477,000
Fair value, ending balance 16,125,000   16,125,000   10,330,000
Investment, Identifier [Axis]: Kahala Aviation, LLC, Subordinated Debt          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     2,966,000   3,360,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     33,911,000 0 0
Gross additions     24,829,000   33,874,000
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     250,000   37,000
Fair value, ending balance 58,990,000   58,990,000   33,911,000
Investment, Identifier [Axis]: Kahala Ireland Opco DAC | Asset Based Financing          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13],[21],[26] 0   0    
Investment, Identifier [Axis]: Kahala Ireland Opco DAC, Subordinated Debt          
Schedule of Investments [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, Equity/Other Investments          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income         83,000
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]: Kaman Corp., Aerospace & Defense 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     58,000    
Fair value, ending balance (1,000)   (1,000)   58,000
Investment, Identifier [Axis]: Kaman Corp., Aerospace & Defense 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,220,000    
Fair value, ending balance 4,065,000   4,065,000   6,220,000
Investment, Identifier [Axis]: Kaseya, Inc., Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,772,000    
Fair value, ending balance 2,887,000   2,887,000   3,772,000
Investment, Identifier [Axis]: Kingpin Intermediate Holdings, LLC, Hotels, Restaurants & Leisure 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,733,000    
Fair value, ending balance 4,248,000   4,248,000   4,733,000
Investment, Identifier [Axis]: Kingpin Intermediate Holdings, LLC, Hotels, Restaurants & Leisure 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,331,000    
Fair value, ending balance 6,000,000   6,000,000   7,331,000
Investment, Identifier [Axis]: Knowledge Pro Buyer, Inc. | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     21,622,000    
Fair value, ending balance 2,663,000 [10],[13]   2,663,000 [10],[13]   21,622,000 [8],[14]
Investment, Identifier [Axis]: Knowledge Pro Buyer, Inc. | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 23,080,000 [10],[13]   23,080,000 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Knowledge Pro Buyer, Inc. | Professional Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     42,173,000    
Fair value, ending balance 41,777,000 [9],[10],[12]   41,777,000 [9],[10],[12]   42,173,000 [7],[8],[11]
Investment, Identifier [Axis]: Kodiak Building Partners, LLC, Building Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,896,000    
Fair value, ending balance         3,896,000
Investment, Identifier [Axis]: LABL, Inc., Containers & Packaging          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,093,000    
Fair value, ending balance         3,093,000
Investment, Identifier [Axis]: LBM Acquisition, LLC, Building Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,867,000   2,867,000    
Investment, Identifier [Axis]: LCM, Ltd. Partnership 16A ER2, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,807,000    
Fair value, ending balance 1,635,000   1,635,000   1,807,000
Investment, Identifier [Axis]: LSF12 Donnelly Bidco, LLC | Machinery          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     18,739,000    
Fair value, ending balance 18,643,000 [9],[10]   18,643,000 [9],[10]   18,739,000 [7],[8]
Investment, Identifier [Axis]: Labrie Environmental Group, LLC | Machinery          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[25]     21,666,000    
Fair value, ending balance [8],[25]         21,666,000
Investment, Identifier [Axis]: Lakeland Tours, LLC | Diversified Consumer Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[12],[15] 2,026,000   2,026,000    
Investment, Identifier [Axis]: Lakeland Tours, LLC | Diversified Consumer Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11],[30]     45,000    
Fair value, ending balance 0 [10],[12],[19],[20]   0 [10],[12],[19],[20]   45,000 [7],[8],[11],[30]
Investment, Identifier [Axis]: Lakeland Tours, LLC | Diversified Consumer Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[11],[30]     1,414,000    
Fair value, ending balance [8],[11],[30]         1,414,000
Investment, Identifier [Axis]: LaserShip, Inc. | Air Freight & Logistics          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [15] 270,000   270,000    
Investment, Identifier [Axis]: LaserShip, Inc. | Ground Transportation          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     838,000    
Fair value, ending balance         838,000
Investment, Identifier [Axis]: Last Dance Intermediate II, LLC | Diversified Telecommunication Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     3,987,000    
Fair value, ending balance 2,944,000 [10],[13]   2,944,000 [10],[13]   3,987,000 [8],[14]
Investment, Identifier [Axis]: Last Dance Intermediate II, LLC | Diversified Telecommunication Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (44,000)    
Fair value, ending balance 15,349,000 [10]   15,349,000 [10]   (44,000) [8],[14]
Investment, Identifier [Axis]: Last Dance Intermediate II, LLC | Diversified Telecommunication Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     18,884,000    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   18,884,000 [7],[8],[11]
Investment, Identifier [Axis]: Last Dance Intermediate II, LLC | Diversified Telecommunication Services 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     19,059,000    
Fair value, ending balance 19,054,000 [9],[10],[12]   19,054,000 [9],[10],[12]   19,059,000 [7],[8],[11]
Investment, Identifier [Axis]: Last Dance Intermediate II, LLC | Diversified Telecommunication Services 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 19,312,000   19,312,000    
Investment, Identifier [Axis]: Lighthouse Intelligence, Ltd. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14],[25]     (154,000)    
Fair value, ending balance 22,085,000 [10],[26]   22,085,000 [10],[26]   (154,000) [8],[14],[25]
Investment, Identifier [Axis]: Lighthouse Intelligence, Ltd. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14],[25]     (110,000)    
Fair value, ending balance (345,000) [10],[13],[26]   (345,000) [10],[13],[26]   (110,000) [8],[14],[25]
Investment, Identifier [Axis]: Lighthouse Intelligence, Ltd. | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[25]     22,370,000    
Fair value, ending balance (246,000) [10],[13],[26]   (246,000) [10],[13],[26]   22,370,000 [8],[25]
Investment, Identifier [Axis]: MGTF Holdco, LLC | Media          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[18],[22]     0    
Fair value, ending balance [8],[16],[17],[18],[22]         0
Investment, Identifier [Axis]: MGTF Holdco, LLC, Equity/Other Investments          
Schedule of Investments [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 Radio Company, LLC | Media          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[18],[30]     11,408,000    
Fair value, ending balance [8],[18],[30]         11,408,000
Investment, Identifier [Axis]: MGTF Radio Company, LLC, Senior Secured First Lien Debt          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     0   1,116,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     11,408,000 31,672,000 31,672,000
Gross additions     0   103,000
Gross reductions     (12,000,000)   0
Realized Gain/(Loss)     (33,020,000)   0
Change in Unrealized Gain (Loss)     33,612,000   (20,367,000)
Fair value, ending balance 0   0   11,408,000
Investment, Identifier [Axis]: MH Sub I, LLC, IT Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,978,000    
Fair value, ending balance 5,184,000   5,184,000   4,978,000
Investment, Identifier [Axis]: MRI Software, LLC | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     52,000    
Fair value, ending balance 2,147,000 [10]   2,147,000 [10]   52,000 [8],[14]
Investment, Identifier [Axis]: MRI Software, LLC | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     11,000    
Fair value, ending balance 6,633,000 [10]   6,633,000 [10]   11,000 [8],[14]
Investment, Identifier [Axis]: MRI Software, LLC | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     2,180,000    
Fair value, ending balance 233,000 [10],[13]   233,000 [10],[13]   2,180,000 [8]
Investment, Identifier [Axis]: MRI Software, LLC | Software 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     6,734,000    
Fair value, ending balance 14,000 [10],[13]   14,000 [10],[13]   6,734,000 [8]
Investment, Identifier [Axis]: MWH Intermediate II, LLC | Capital Markets 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 8,945,000   8,945,000    
Investment, Identifier [Axis]: MWH Intermediate II, LLC | Capital Markets 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 930,000   930,000    
Investment, Identifier [Axis]: MWH Intermediate II, LLC | Capital Markets 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 15,215,000   15,215,000    
Investment, Identifier [Axis]: MWH Intermediate II, LLC | Financial Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     1,941,000    
Fair value, ending balance [8],[14]         1,941,000
Investment, Identifier [Axis]: MWH Intermediate II, LLC | Financial Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (13,000)    
Fair value, ending balance [8],[14]         (13,000)
Investment, Identifier [Axis]: MWH Intermediate II, LLC | Financial Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     15,284,000    
Fair value, ending balance [7],[8]         15,284,000
Investment, Identifier [Axis]: Mandrake Bidco, Inc. | Machinery 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Mandrake Bidco, Inc. | Machinery 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     55,557,000    
Fair value, ending balance 55,557,000 [9],[10],[12]   55,557,000 [9],[10],[12]   55,557,000 [7],[8],[11]
Investment, Identifier [Axis]: Manna Pro Products, LLC | Food Products 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 3,237,000   3,237,000    
Investment, Identifier [Axis]: Manna Pro Products, LLC | Food Products 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (135,000)   (135,000)    
Investment, Identifier [Axis]: Manna Pro Products, LLC | Food Products 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[12] 1,543,000   1,543,000    
Investment, Identifier [Axis]: Manna Pro Products, LLC | Food Products 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[12] 5,550,000   5,550,000    
Investment, Identifier [Axis]: Manna Pro Products, LLC | Food Products 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[12] 19,574,000   19,574,000    
Investment, Identifier [Axis]: Manna Pro Products, LLC | Specialty Retail 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     3,341,000    
Fair value, ending balance [8]         3,341,000
Investment, Identifier [Axis]: Manna Pro Products, LLC | Specialty Retail 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (430,000)    
Fair value, ending balance [8],[14]         (430,000)
Investment, Identifier [Axis]: Manna Pro Products, LLC | Specialty Retail 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     1,593,000    
Fair value, ending balance [8]         1,593,000
Investment, Identifier [Axis]: Manna Pro Products, LLC | Specialty Retail 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     5,729,000    
Fair value, ending balance [8]         5,729,000
Investment, Identifier [Axis]: Manna Pro Products, LLC | Specialty Retail 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     20,204,000    
Fair value, ending balance [8]         20,204,000
Investment, Identifier [Axis]: Maravai Intermediate Holdings, LLC | Life Sciences Tools & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13],[26] (42,000)   (42,000)    
Investment, Identifier [Axis]: Maravai Intermediate Holdings, LLC | Life Sciences Tools & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[12],[26] 14,077,000   14,077,000    
Investment, Identifier [Axis]: Max US Bidco, Inc., Food Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,755,000    
Fair value, ending balance 4,438,000   4,438,000   3,755,000
Investment, Identifier [Axis]: McDonald Worley, P.C. | Professional Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[19],[20] 10,828,000   10,828,000    
Investment, Identifier [Axis]: McDonald Worley, P.C. | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14],[30]     6,513,000    
Fair value, ending balance 4,845,000 [10],[13],[15]   4,845,000 [10],[13],[15]   6,513,000 [8],[14],[30]
Investment, Identifier [Axis]: McDonald Worley, P.C. | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     10,264,000    
Fair value, ending balance [8],[16],[17]         10,264,000
Investment, Identifier [Axis]: Medical Management Resource Group, LLC | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     744,000    
Fair value, ending balance (26,000) [10],[13]   (26,000) [10],[13]   744,000 [8],[14]
Investment, Identifier [Axis]: Medical Management Resource Group, LLC | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     9,184,000    
Fair value, ending balance 9,136,000 [9],[10]   9,136,000 [9],[10]   9,184,000 [7],[8]
Investment, Identifier [Axis]: Medical Management Resource Group, LLC | Health Care Providers & Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     22,233,000    
Fair value, ending balance 22,117,000 [9],[10]   22,117,000 [9],[10]   22,233,000 [7],[8]
Investment, Identifier [Axis]: Megavolt Borrower, LLC | Construction & Engineering          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     36,989,000    
Fair value, ending balance 36,803,000 [9],[10],[12]   36,803,000 [9],[10],[12]   36,989,000 [7],[8],[11]
Investment, Identifier [Axis]: Merlin Buyer, Inc., Machinery          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,118,000    
Fair value, ending balance 2,503,000   2,503,000   1,118,000
Investment, Identifier [Axis]: Mermaid Bidco Inc, IT Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,481,000    
Fair value, ending balance         7,481,000
Investment, Identifier [Axis]: Mermaid Bidco, Inc. , IT Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 7,177,000   7,177,000    
Investment, Identifier [Axis]: Michael Baker International, LLC | Construction & Engineering          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 17,231,000   17,231,000    
Investment, Identifier [Axis]: Michael Baker International, LLC | Professional Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     18,223,000    
Fair value, ending balance [8]         18,223,000
Investment, Identifier [Axis]: Midwest Can Company, LLC | Containers & Packaging          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     27,902,000    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   27,902,000 [7],[8],[11]
Investment, Identifier [Axis]: Midwest Can Company, LLC | Containers & Packaging 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 26,494,000   26,494,000    
Investment, Identifier [Axis]: Mirra-Primeaccess Holdings, LLC | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     7,316,000    
Fair value, ending balance 60,959,000 [10]   60,959,000 [10]   7,316,000 [8],[14]
Investment, Identifier [Axis]: Mirra-Primeaccess Holdings, LLC | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     61,279,000    
Fair value, ending balance 7,316,000 [10],[13]   7,316,000 [10],[13]   61,279,000 [8]
Investment, Identifier [Axis]: Monogram Food Solutions, LLC, Food Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,088,000    
Fair value, ending balance 2,074,000   2,074,000   2,088,000
Investment, Identifier [Axis]: Motor Vehicle Software Corp. | Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[31]     1,077,000    
Fair value, ending balance 1,077,000 [10],[19],[20],[32]   1,077,000 [10],[19],[20],[32]   1,077,000 [8],[16],[17],[31]
Investment, Identifier [Axis]: Multi-Color Corp., Containers & Packaging          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,151,000   2,151,000    
Investment, Identifier [Axis]: Multi-Color Corp., Containers & Packaging 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 44,000   44,000    
Investment, Identifier [Axis]: Multi-Color Corp., Containers & Packaging 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 688,000   688,000    
Investment, Identifier [Axis]: Multi-Color Corp., Containers & Packaging 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,000   2,000    
Investment, Identifier [Axis]: Muth Mirror Systems, LLC | Automobile Components (1)          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[19],[20],[23] 0   0    
Investment, Identifier [Axis]: Muth Mirror Systems, LLC | Automobile Components (2)          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[19],[20],[23] 0   0    
Investment, Identifier [Axis]: Muth Mirror Systems, LLC | Automobile Components 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14],[30]     396,000    
Fair value, ending balance (11,000) [10],[13],[15]   (11,000) [10],[13],[15]   396,000 [8],[14],[30]
Investment, Identifier [Axis]: Muth Mirror Systems, LLC | Automobile Components 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[30]     7,624,000    
Fair value, ending balance 4,549,000 [10],[15]   4,549,000 [10],[15]   7,624,000 [8],[30]
Investment, Identifier [Axis]: Muth Mirror Systems, LLC | Automobile Components 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[22]     0    
Fair value, ending balance [8],[16],[17],[22]         0
Investment, Identifier [Axis]: Muth Mirror Systems, LLC | Automobile Components 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[22]     0    
Fair value, ending balance [8],[16],[17],[22]         0
Investment, Identifier [Axis]: Neptune Bidco US, Inc., Interactive Media & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     579,000    
Fair value, ending balance         579,000
Investment, Identifier [Axis]: NewStar Arlington Senior Loan Program, LLC 14-1A FR | Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[17],[24],[25]     4,322,000    
Fair value, ending balance 3,248,000 [10],[20],[26],[27]   3,248,000 [10],[20],[26],[27]   4,322,000 [8],[17],[24],[25]
Investment, Identifier [Axis]: NewStar Arlington Senior Loan Program, LLC 14-1A FR, Collateralized Securities          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     385,000   794,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,322,000 4,237,000 4,237,000
Gross additions     28,000   48,000
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     (1,102,000)   37,000
Fair value, ending balance 3,248,000   3,248,000   4,322,000
Investment, Identifier [Axis]: NewStar Arlington Senior Loan Program, LLC 14-1A SUB | Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[17],[24],[25],[33]     0    
Fair value, ending balance 183,000 [10],[20],[26],[27],[34]   183,000 [10],[20],[26],[27],[34]   0 [8],[17],[24],[25],[33]
Investment, Identifier [Axis]: NewStar Arlington Senior Loan Program, LLC 14-1A SUB, Collateralized Securities          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     0   (88,000)
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     0 2,170,000 2,170,000
Gross additions     0   0
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     183,000   (2,170,000)
Fair value, ending balance 183,000   183,000   0
Investment, Identifier [Axis]: NewStar Fairfield Fund CLO, Ltd. 2015-1RA SUB | Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[20],[26],[27],[34] 467,000   467,000    
Investment, Identifier [Axis]: Newstar Fairfield Fund CLO, Ltd. 2015-1RA F, Collateralized Securities          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income         17,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     0 2,457,000 2,457,000
Gross additions         3,000
Gross reductions         (2,457,000)
Realized Gain/(Loss)         137,000
Change in Unrealized Gain (Loss)         (140,000)
Fair value, ending balance         0
Investment, Identifier [Axis]: Newstar Fairfield Fund CLO, Ltd. 2015-1RA SUB | Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[17],[24],[25],[33]     477,000    
Fair value, ending balance [8],[17],[24],[25],[33]         477,000
Investment, Identifier [Axis]: Newstar Fairfield Fund CLO, Ltd. 2015-1RA SUB, Collateralized Securities          
Schedule of Investments [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     477,000 1,208,000 1,208,000
Gross additions     0   0
Gross reductions     (12,000)   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     2,000   (731,000)
Fair value, ending balance 467,000   467,000   477,000
Investment, Identifier [Axis]: Nexus Buyer, LLC , Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 4,750,000   4,750,000    
Investment, Identifier [Axis]: Nexus Buyer, LLC, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,889,000    
Fair value, ending balance         4,889,000
Investment, Identifier [Axis]: Norvax, LLC | Insurance 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     354,000    
Fair value, ending balance 229,000 [10]   229,000 [10]   354,000 [8]
Investment, Identifier [Axis]: Norvax, LLC | Insurance 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     228,000    
Fair value, ending balance 0 [10],[15]   0 [10],[15]   228,000 [8]
Investment, Identifier [Axis]: Nouryon Finance B.V., Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,202,000    
Fair value, ending balance 2,191,000   2,191,000   2,202,000
Investment, Identifier [Axis]: ORG GC Holdings, LLC | Professional Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[27] 10,112,000   10,112,000    
Investment, Identifier [Axis]: ORG GC Holdings, LLC | Professional Services (1)          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[19],[20],[23],[27] 0   0    
Investment, Identifier [Axis]: ORG GC Holdings, LLC | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[24]     10,111,000    
Fair value, ending balance 2,433,000 [10],[15],[27]   2,433,000 [10],[15],[27]   10,111,000 [8],[24]
Investment, Identifier [Axis]: ORG GC Holdings, LLC | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[24],[30]     2,810,000    
Fair value, ending balance 0 [10],[19],[20],[23],[27]   0 [10],[19],[20],[23],[27]   2,810,000 [8],[24],[30]
Investment, Identifier [Axis]: ORG GC Holdings, LLC | Professional Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[22],[24]     0    
Fair value, ending balance [8],[16],[17],[22],[24]         0
Investment, Identifier [Axis]: ORG GC Holdings, LLC | Professional Services 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[22],[24]     0    
Fair value, ending balance [8],[16],[17],[22],[24]         0
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Equity/Other Investments 1          
Schedule of Investments [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   0
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Equity/Other Investments 2          
Schedule of Investments [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   0
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Equity/Other Investments 3          
Schedule of Investments [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]: ORG GC Holdings, LLC, Senior Secured First Lien Debt          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     530,000   1,124,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     10,111,000 10,112,000 10,112,000
Gross additions     (1,000)   (3,000)
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     2,000   2,000
Fair value, ending balance 10,112,000   10,112,000   10,111,000
Investment, Identifier [Axis]: ORG GC Holdings, LLC, Senior Secured Second Lien Debt          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     0   576,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,810,000 4,999,000 4,999,000
Gross additions     0   578,000
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     (377,000)   (2,767,000)
Fair value, ending balance 2,433,000   2,433,000   2,810,000
Investment, Identifier [Axis]: OSV Thunderbold Topco, Inc. | Professional Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 4,185,000   4,185,000    
Investment, Identifier [Axis]: OSV Thunderbold Topco, Inc. | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[19],[20] 589,000   589,000    
Investment, Identifier [Axis]: Obra Capital, Inc. | Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 4,095,000   4,095,000    
Investment, Identifier [Axis]: Obra Capital, Inc. | Capital Markets 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[19],[20] 332,000   332,000    
Investment, Identifier [Axis]: Odessa Technologies, Inc. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Odessa Technologies, Inc. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     20,236,000    
Fair value, ending balance 20,130,000 [9],[10]   20,130,000 [9],[10]   20,236,000 [7],[8]
Investment, Identifier [Axis]: Omnia Partners, LLC , Commercial Services & Supplies          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,171,000    
Fair value, ending balance         6,171,000
Investment, Identifier [Axis]: Omnia Partners, LLC, Commercial Services & Supplies          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 6,124,000   6,124,000    
Investment, Identifier [Axis]: OneDigital Borrower, LLC Insurance          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,894,000   2,894,000    
Investment, Identifier [Axis]: OneSource Virtual, Inc. | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (13,000)   (13,000)    
Investment, Identifier [Axis]: OneSource Virtual, Inc. | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 18,473,000   18,473,000    
Investment, Identifier [Axis]: PG&E Corp., Electric Utilities          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     9,412,000    
Fair value, ending balance 9,496,000   9,496,000   9,412,000
Investment, Identifier [Axis]: PODS, LLC, Air Freight & Logistics          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,343,000    
Fair value, ending balance 3,886,000   3,886,000   7,343,000
Investment, Identifier [Axis]: PODS, LLC, Air Freight & Logistics 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,926,000   2,926,000    
Investment, Identifier [Axis]: Palmdale Oil Co., LLC | Oil, Gas & Consumable Fuels          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     3,335,000    
Fair value, ending balance [8]         3,335,000
Investment, Identifier [Axis]: Palmdale Oil Co., LLC | Oil, Gas & Consumable Fuels 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 4,318,000   4,318,000    
Investment, Identifier [Axis]: Palmdale Oil Co., LLC | Oil, Gas & Consumable Fuels 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (15,000)   (15,000)    
Investment, Identifier [Axis]: Peer Holding III B.V., Broadline Retail          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,961,000    
Fair value, ending balance 5,917,000   5,917,000   5,961,000
Investment, Identifier [Axis]: PennantPark Credit Opportunities Fund II, LP | Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [16],[17],[24],[25]     552,000    
Fair value, ending balance 653,000 [19],[20],[26],[27]   653,000 [19],[20],[26],[27]   552,000 [16],[17],[24],[25]
Investment, Identifier [Axis]: PennantPark Credit Opportunities Fund II, LP, Equity/Other Investments          
Schedule of Investments [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     552,000 603,000 603,000
Gross additions     0   0
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     101,000   (51,000)
Fair value, ending balance 653,000   653,000   552,000
Investment, Identifier [Axis]: Peraton Corp Communications Equipment          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 1,795,000   1,795,000    
Investment, Identifier [Axis]: Peraton Corp., Communications Equipment          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,636,000    
Fair value, ending balance 5,181,000   5,181,000   7,636,000
Investment, Identifier [Axis]: PetSmart, LLC, Specialty Retail          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,442,000    
Fair value, ending balance 2,444,000   2,444,000   2,442,000
Investment, Identifier [Axis]: PetVet Care Centers, LLC | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     210,000    
Fair value, ending balance 806,000 [10],[13]   806,000 [10],[13]   210,000 [8],[14]
Investment, Identifier [Axis]: PetVet Care Centers, LLC | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     28,841,000    
Fair value, ending balance 27,127,000 [9],[10],[12]   27,127,000 [9],[10],[12]   28,841,000 [7],[8],[11]
Investment, Identifier [Axis]: Pie Buyer, Inc. | Consumer Staples Distribution & Retail 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     2,323,000    
Fair value, ending balance 2,194,000 [10]   2,194,000 [10]   2,323,000 [8]
Investment, Identifier [Axis]: Pie Buyer, Inc. | Consumer Staples Distribution & Retail 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     7,787,000    
Fair value, ending balance 7,355,000 [9],[10]   7,355,000 [9],[10]   7,787,000 [7],[8]
Investment, Identifier [Axis]: Pie Buyer, Inc. | Consumer Staples Distribution & Retail 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     2,042,000    
Fair value, ending balance 1,929,000 [9],[10]   1,929,000 [9],[10]   2,042,000 [7],[8]
Investment, Identifier [Axis]: Pie Buyer, Inc. | Consumer Staples Distribution & Retail 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     35,981,000    
Fair value, ending balance 33,982,000 [9],[10],[12]   33,982,000 [9],[10],[12]   35,981,000 [7],[8],[11]
Investment, Identifier [Axis]: Pie Buyer, Inc. | Consumer Staples Distribution & Retail 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     2,660,000    
Fair value, ending balance 2,513,000 [9],[10],[12]   2,513,000 [9],[10],[12]   2,660,000 [7],[8],[11]
Investment, Identifier [Axis]: Pluralsight, LLC | Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     0    
Fair value, ending balance 0 [10],[19],[20]   0 [10],[19],[20]   0 [8],[16],[17]
Investment, Identifier [Axis]: Pluralsight, LLC | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     4,600,000    
Fair value, ending balance 4,563,000 [10]   4,563,000 [10]   4,600,000 [8]
Investment, Identifier [Axis]: Pluralsight, LLC | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     7,422,000    
Fair value, ending balance 2,318,000 [10]   2,318,000 [10]   7,422,000 [8]
Investment, Identifier [Axis]: Pluralsight, LLC | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     2,336,000    
Fair value, ending balance (35,000) [10],[13]   (35,000) [10],[13]   2,336,000 [8]
Investment, Identifier [Axis]: Pluralsight, LLC | Software 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (14,000)   (14,000)    
Investment, Identifier [Axis]: Pluralsight, LLC | Software 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[15] 846,000   846,000    
Investment, Identifier [Axis]: Pluto Acquisition I, Inc. | Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 3,345,000   3,345,000    
Investment, Identifier [Axis]: Pluto Acquisition I, Inc. | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,337,000    
Fair value, ending balance 33,540,000 [9],[10]   33,540,000 [9],[10]   3,337,000
Investment, Identifier [Axis]: Pluto Acquisition I, Inc. | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     32,134,000    
Fair value, ending balance [7],[8]         32,134,000
Investment, Identifier [Axis]: Pluto Acquisition I, Inc., Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,984,000    
Fair value, ending balance 8,937,000   8,937,000   7,984,000
Investment, Identifier [Axis]: Point Broadband Acquisition, LLC | Diversified Telecommunication Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[22]     124,000    
Fair value, ending balance 124,000 [10],[19],[20],[23]   124,000 [10],[19],[20],[23]   124,000 [8],[16],[17],[22]
Investment, Identifier [Axis]: Point Broadband Acquisition, LLC | Diversified Telecommunication Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[22]     4,935,000    
Fair value, ending balance 4,935,000 [10],[19],[20],[23]   4,935,000 [10],[19],[20],[23]   4,935,000 [8],[16],[22]
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC | Asset Based Financing          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[17],[18],[22],[28]     128,252,000    
Fair value, ending balance 138,475,000 [10],[20],[21],[23],[29]   138,475,000 [10],[20],[21],[23],[29]   128,252,000 [8],[17],[18],[22],[28]
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC | Asset Based Financing 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14],[18],[28]     34,000,000    
Fair value, ending balance 0 [10],[13],[21],[29]   0 [10],[13],[21],[29]   34,000,000 [8],[14],[18],[28]
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC | Asset Based Financing 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14],[18],[28]     0    
Fair value, ending balance 31,000,000 [10],[13],[21],[29]   31,000,000 [10],[13],[21],[29]   0 [8],[14],[18],[28]
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC | Asset Based Financing 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[18],[28]     62,601,000    
Fair value, ending balance 62,600,000 [10],[21],[29]   62,600,000 [10],[21],[29]   62,601,000 [8],[18],[28]
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Equity/Other Investments          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     5,840,000   11,274,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     128,252,000 119,233,000 119,233,000
Gross additions     0   8,926,000
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     10,223,000   93,000
Fair value, ending balance 138,475,000   138,475,000   128,252,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Subordinated Debt 1          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     3,613,000   7,595,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     62,601,000 62,599,000 62,599,000
Gross additions     11,000   (2,000)
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     (12,000)   4,000
Fair value, ending balance 62,600,000   62,600,000   62,601,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Subordinated Debt 2          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     1,632,000   3,864,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     34,000,000 35,000,000 35,000,000
Gross additions     14,000,000   23,000,000
Gross reductions     (17,000,000)   (24,000,000)
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     0   0
Fair value, ending balance 31,000,000   31,000,000   34,000,000
Investment, Identifier [Axis]: Post Road Equipment Finance, LLC, Subordinated Debt 3          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     40,000   190,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     0 3,000,000 3,000,000
Gross additions     3,000,000   10,000,000
Gross reductions     (3,015,000)   (13,050,000)
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     15,000   50,000
Fair value, ending balance 0   0   0
Investment, Identifier [Axis]: Pregis TopCo, LLC, Containers & Packaging          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,712,000    
Fair value, ending balance 6,643,000   6,643,000   6,712,000
Investment, Identifier [Axis]: Pretzel Parent, Inc, Entertainment          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 3,278,000   3,278,000    
Investment, Identifier [Axis]: Pretzel Parent, Inc., Entertainment          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,426,000    
Fair value, ending balance         3,426,000
Investment, Identifier [Axis]: Primo Brands Corp., Beverages          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 6,144,000   6,144,000    
Investment, Identifier [Axis]: ProAmpac PG Borrower, LLC, Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 6,931,000   6,931,000    
Investment, Identifier [Axis]: Proofpoint, Inc, Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 6,344,000   6,344,000    
Investment, Identifier [Axis]: Proofpoint, Inc., Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,644,000    
Fair value, ending balance         6,644,000
Investment, Identifier [Axis]: Pug, LLC, Entertainment          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,474,000    
Fair value, ending balance 4,978,000   4,978,000   2,474,000
Investment, Identifier [Axis]: Questex, Inc. | Media 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (32,000)    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   (32,000) [8],[14]
Investment, Identifier [Axis]: Questex, Inc. | Media 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[11]     14,703,000    
Fair value, ending balance 14,873,000 [10],[12]   14,873,000 [10],[12]   14,703,000 [8],[11]
Investment, Identifier [Axis]: Quikrete Holdings, Inc., Construction Materials 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,517,000    
Fair value, ending balance 4,477,000   4,477,000   4,517,000
Investment, Identifier [Axis]: Quikrete Holdings, Inc., Construction Materials 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,538,000    
Fair value, ending balance 2,515,000   2,515,000   2,538,000
Investment, Identifier [Axis]: RMP Group, Inc. | Health Care Technology          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[22]     246,000    
Fair value, ending balance 43,000 [10],[19],[20],[23]   43,000 [10],[19],[20],[23]   246,000 [8],[16],[17],[22]
Investment, Identifier [Axis]: Radiology Partners, Inc, Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 7,543,000   7,543,000    
Investment, Identifier [Axis]: Radiology Partners, Inc., Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,570,000    
Fair value, ending balance         7,570,000
Investment, Identifier [Axis]: Raven Acquisition Holdings, LLC, Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     9,754,000    
Fair value, ending balance 9,542,000   9,542,000   9,754,000
Investment, Identifier [Axis]: Raven Acquisition Holdings, LLC, Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,000    
Fair value, ending balance (10,000)   (10,000)   2,000
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 [8]     5,605,000    
Fair value, ending balance 5,311,000 [10]   5,311,000 [10]   5,605,000 [8]
Investment, Identifier [Axis]: Reagent Chemical and Research, LLC | Chemicals 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Reagent Chemical and Research, LLC | Chemicals 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     44,417,000    
Fair value, ending balance 42,323,000 [9],[10],[12]   42,323,000 [9],[10],[12]   44,417,000 [7],[8],[11]
Investment, Identifier [Axis]: Realtruck Group, Inc. Automobile Components 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 5,129,000   5,129,000    
Investment, Identifier [Axis]: Realtruck Group, Inc. Automobile Components 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,751,000   2,751,000    
Investment, Identifier [Axis]: Realtruck Group, Inc. Automobile Components 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,943,000   2,943,000    
Investment, Identifier [Axis]: Recess Holdings, Inc., Household Durables          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,373,000    
Fair value, ending balance 3,315,000   3,315,000   5,373,000
Investment, Identifier [Axis]: Red Planet Borrower, LLC, Media          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,506,000    
Fair value, ending balance 2,700,000   2,700,000   7,506,000
Investment, Identifier [Axis]: Relativity Oda, LLC | Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     7,717,000    
Fair value, ending balance [7],[8]         7,717,000
Investment, Identifier [Axis]: Renaissance Holdings Corp., Diversified Consumer Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,613,000    
Fair value, ending balance 3,256,000   3,256,000   3,613,000
Investment, Identifier [Axis]: Resideo Funding, Inc., Building Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,934,000    
Fair value, ending balance 1,917,000   1,917,000   1,934,000
Investment, Identifier [Axis]: Resilience Parent, LLC | Electrical Equipment          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10] 9,634,000   9,634,000    
Investment, Identifier [Axis]: Resolute Investment Managers, Inc. | Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[19],[20] 112,000   112,000    
Investment, Identifier [Axis]: Resolute Investment Managers, Inc. | Financial Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     2,022,000    
Fair value, ending balance [8],[16],[17]         2,022,000
Investment, Identifier [Axis]: Resolute Investment Managers, Inc., Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 55,000   55,000    
Investment, Identifier [Axis]: Resolute Investment Managers, Inc., Financial Services          
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]: Rialto Management Group, LLC | Capital Markets 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 0   0    
Investment, Identifier [Axis]: Rialto Management Group, LLC | Capital Markets 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 20,178,000   20,178,000    
Investment, Identifier [Axis]: Rialto Management Group, LLC | Financial Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance [8],[14]         0
Investment, Identifier [Axis]: Rialto Management Group, LLC | Financial Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     20,178,000    
Fair value, ending balance [7],[8],[11]         20,178,000
Investment, Identifier [Axis]: Rithm Capital Corp., Mortgage Real Estate Investment Trusts (REITs)          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 3,009,000   3,009,000    
Investment, Identifier [Axis]: Rithum Holdings, Inc., Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,977,000    
Fair value, ending balance 4,671,000   4,671,000   4,977,000
Investment, Identifier [Axis]: Roadsafe Holdings, Inc. | Construction & Engineering 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 5,345,000   5,345,000    
Investment, Identifier [Axis]: Roadsafe Holdings, Inc. | Construction & Engineering 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 4,973,000   4,973,000    
Investment, Identifier [Axis]: Roadsafe Holdings, Inc. | Construction & Engineering 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 8,750,000   8,750,000    
Investment, Identifier [Axis]: Roadsafe Holdings, Inc. | Construction & Engineering 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12] 789,000   789,000    
Investment, Identifier [Axis]: Roadsafe Holdings, Inc. | Transportation Infrastructure 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     7,286,000    
Fair value, ending balance [7],[8]         7,286,000
Investment, Identifier [Axis]: Roadsafe Holdings, Inc. | Transportation Infrastructure 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     6,779,000    
Fair value, ending balance [7],[8]         6,779,000
Investment, Identifier [Axis]: Roadsafe Holdings, Inc. | Transportation Infrastructure 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     11,930,000    
Fair value, ending balance [7],[8],[11]         11,930,000
Investment, Identifier [Axis]: Roadsafe Holdings, Inc. | Transportation Infrastructure 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     1,075,000    
Fair value, ending balance [7],[8],[11]         1,075,000
Investment, Identifier [Axis]: Roper Industrial Products Investment Co., LLC, Industrial Conglomerates          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,973,000    
Fair value, ending balance         4,973,000
Investment, Identifier [Axis]: S&S Holdings, LLC, Textiles, Apparel & luxury goods          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,668,000    
Fair value, ending balance 4,590,000   4,590,000   4,668,000
Investment, Identifier [Axis]: SCIH Salt Holdings, Inc. | Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     315,000    
Fair value, ending balance (15,000) [10],[13]   (15,000) [10],[13]   315,000 [8],[14]
Investment, Identifier [Axis]: Saab Purchaser, Inc. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (166,000)    
Fair value, ending balance (166,000) [10],[13]   (166,000) [10],[13]   (166,000) [8],[14]
Investment, Identifier [Axis]: Saab Purchaser, Inc. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (22,000)    
Fair value, ending balance (22,000) [10],[13]   (22,000) [10],[13]   (22,000) [8],[14]
Investment, Identifier [Axis]: Saab Purchaser, Inc. | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     17,705,000    
Fair value, ending balance 17,705,000 [9],[10]   17,705,000 [9],[10]   17,705,000 [7],[8]
Investment, Identifier [Axis]: Saranac CLO, Ltd. 20-8A E, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,095,000    
Fair value, ending balance 618,000   618,000   1,095,000
Investment, Identifier [Axis]: Saturn SHC Buyer Holdings, Inc. | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (1,290,000)    
Fair value, ending balance (2,580,000) [10],[13]   (2,580,000) [10],[13]   (1,290,000) [8],[14]
Investment, Identifier [Axis]: Saturn SHC Buyer Holdings, Inc. | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     33,449,000    
Fair value, ending balance 29,733,000 [9],[10]   29,733,000 [9],[10]   33,449,000 [7],[8]
Investment, Identifier [Axis]: Saturn SHC Buyer Holdings, Inc. | Health Care Providers & Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     11,693,000    
Fair value, ending balance 10,394,000 [9],[10]   10,394,000 [9],[10]   11,693,000 [7],[8]
Investment, Identifier [Axis]: Saturn Sound Bidco, Ltd. | Aerospace & Defense 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13],[26] 0   0    
Investment, Identifier [Axis]: Saturn Sound Bidco, Ltd. | Aerospace & Defense 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10],[12],[26] 24,800,000   24,800,000    
Investment, Identifier [Axis]: Saturn Sound Bidco, Ltd. | Trading Companies & Distributors 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14],[25]     (38,000)    
Fair value, ending balance [8],[14],[25]         (38,000)
Investment, Identifier [Axis]: Saturn Sound Bidco, Ltd. | Trading Companies & Distributors 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11],[25]     24,589,000    
Fair value, ending balance [7],[8],[11],[25]         24,589,000
Investment, Identifier [Axis]: Sedgwick Claims Management Services, Inc., Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,239,000    
Fair value, ending balance 7,088,000   7,088,000   7,239,000
Investment, Identifier [Axis]: Sharp Services, LLC, Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,023,000    
Fair value, ending balance         3,023,000
Investment, Identifier [Axis]: Sherlock Buyer Corp. | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Sherlock Buyer Corp. | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     15,558,000    
Fair value, ending balance 15,476,000 [9],[10],[12]   15,476,000 [9],[10],[12]   15,558,000 [7],[8],[11]
Investment, Identifier [Axis]: Siena Capital Finance, LLC | Asset Based Financing          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[17],[18]     77,728,000    
Fair value, ending balance 72,500,000 [10],[21]   72,500,000 [10],[21]   77,728,000 [8],[17],[18]
Investment, Identifier [Axis]: Siena Capital Finance, LLC | Asset Based Financing 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[18]     77,500,000    
Fair value, ending balance 85,668,000 [10],[20],[21]   85,668,000 [10],[20],[21]   77,500,000 [8],[18]
Investment, Identifier [Axis]: Siena Capital Finance, LLC, Equity/Other Investments          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     5,525,000   13,727,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     77,728,000 77,310,000 77,310,000
Gross additions     0   0
Gross reductions     0   0
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     7,940,000   418,000
Fair value, ending balance 85,668,000   85,668,000   77,728,000
Investment, Identifier [Axis]: Siena Capital Finance, LLC, Subordinated Debt          
Schedule of Investments [Line Items]          
Amount of dividends and interest included in income     5,099,000   7,109,000
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     77,500,000 49,500,000 49,500,000
Gross additions     7,510,000   27,990,000
Gross reductions     (12,500,000)   0
Realized Gain/(Loss)     (9,000)   0
Change in Unrealized Gain (Loss)     (1,000)   10,000
Fair value, ending balance 72,500,000   72,500,000   77,500,000
Investment, Identifier [Axis]: Simplifi Holdings, Inc. | Media 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     516,000    
Fair value, ending balance 1,926,000 [10],[13]   1,926,000 [10],[13]   516,000 [8],[14]
Investment, Identifier [Axis]: Simplifi Holdings, Inc. | Media 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     49,524,000    
Fair value, ending balance 49,267,000 [9],[10]   49,267,000 [9],[10]   49,524,000 [7],[8]
Investment, Identifier [Axis]: SitusAMC Holdings Corp. | Financial Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     52,130,000    
Fair value, ending balance 51,868,000 [9],[10],[12]   51,868,000 [9],[10],[12]   52,130,000 [7],[8],[11]
Investment, Identifier [Axis]: Skillsoft Corp. | Professional Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [16]     116,000    
Fair value, ending balance [16]         116,000
Investment, Identifier [Axis]: Smile Brands, Inc. | Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     0    
Fair value, ending balance 0 [10],[15]   0 [10],[15]   0 [8],[16],[17]
Investment, Identifier [Axis]: Smile Brands, Inc. | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[19],[20] 0   0    
Investment, Identifier [Axis]: Smile Brands, Inc. | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     9,000    
Fair value, ending balance [8]         9,000
Investment, Identifier [Axis]: Sonrava Health Holdings, LLC, Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,754,000    
Fair value, ending balance         1,754,000
Investment, Identifier [Axis]: Sonrava Health Holdings, LLC, Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,617,000    
Fair value, ending balance         1,617,000
Investment, Identifier [Axis]: Sonrava Health Holdings, LLC, Health Care Providers & Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     311,000    
Fair value, ending balance         311,000
Investment, Identifier [Axis]: Sotera Health Holdings, LLC, Life Sciences Tools & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,442,000    
Fair value, ending balance 7,391,000   7,391,000   7,442,000
Investment, Identifier [Axis]: Sound Point CLO, Ltd. 17-2A E, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     1,820,000    
Fair value, ending balance 1,494,000   1,494,000   1,820,000
Investment, Identifier [Axis]: Sound Point CLO, Ltd. 18-3A D, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     819,000    
Fair value, ending balance 605,000   605,000   819,000
Investment, Identifier [Axis]: Specialty Building Products Holdings, LLC, Building Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,583,000    
Fair value, ending balance 5,755,000   5,755,000   4,583,000
Investment, Identifier [Axis]: Squan Holding Corp. | Wireless Telecommunication Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     0    
Fair value, ending balance 0 [10],[19],[20]   0 [10],[19],[20]   0 [8],[16],[17]
Investment, Identifier [Axis]: Staples, Inc., Business Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     704,292,000    
Fair value, ending balance         704,292,000
Investment, Identifier [Axis]: Staples, Inc., Specialty Retail          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,799,000    
Fair value, ending balance 2,727,000   2,727,000   2,799,000
Investment, Identifier [Axis]: Starlight Parent, LLC, Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,472,000    
Fair value, ending balance 2,252,000   2,252,000   5,472,000
Investment, Identifier [Axis]: Stonepeak Nile Parent, LLC , Air Freight & Logistics          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,373,000    
Fair value, ending balance         4,373,000
Investment, Identifier [Axis]: Stonepeak Nile Parent, LLC, Air Freight & Logistics          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 4,350,000   4,350,000    
Investment, Identifier [Axis]: Striper Buyer, LLC | Containers & Packaging          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     16,652,000    
Fair value, ending balance 14,501,000 [9],[10]   14,501,000 [9],[10]   16,652,000 [7],[8]
Investment, Identifier [Axis]: SunMed Group Holdings, LLC | Health Care Equipment & Supplies 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: SunMed Group Holdings, LLC | Health Care Equipment & Supplies 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     12,438,000    
Fair value, ending balance 12,373,000 [9],[10]   12,373,000 [9],[10]   12,438,000 [7],[8]
Investment, Identifier [Axis]: Symphony CLO, Ltd. 2012-9A ER2, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,779,000    
Fair value, ending balance 2,478,000   2,478,000   2,779,000
Investment, Identifier [Axis]: TEI Intermediate, LLC | Commercial Services & Supplies 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     932,000    
Fair value, ending balance 5,235,000 [10],[13]   5,235,000 [10],[13]   932,000 [8],[14]
Investment, Identifier [Axis]: TEI Intermediate, LLC | Commercial Services & Supplies 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     859,000    
Fair value, ending balance 384,000 [10],[13]   384,000 [10],[13]   859,000 [8],[14]
Investment, Identifier [Axis]: TEI Intermediate, LLC | Commercial Services & Supplies 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     23,015,000    
Fair value, ending balance 23,349,000 [9],[10],[12]   23,349,000 [9],[10],[12]   23,015,000 [7],[8],[11]
Investment, Identifier [Axis]: Tamko Building Products, Inc., Building Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 1,358,000   1,358,000    
Investment, Identifier [Axis]: Tax Defense Network, LLC | Diversified Consumer Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[30]     0    
Fair value, ending balance 0 [10],[15]   0 [10],[15]   0 [8],[30]
Investment, Identifier [Axis]: Tax Defense Network, LLC | Diversified Consumer Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[30]     0    
Fair value, ending balance 0 [10],[15]   0 [10],[15]   0 [8],[30]
Investment, Identifier [Axis]: Tax Defense Network, LLC | Diversified Consumer Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[30]     6,022,000    
Fair value, ending balance 6,391,000 [10],[15]   6,391,000 [10],[15]   6,022,000 [8],[30]
Investment, Identifier [Axis]: Tax Defense Network, LLC | Diversified Consumer Services 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     0    
Fair value, ending balance 0 [10],[19],[20]   0 [10],[19],[20]   0 [8],[16],[17]
Investment, Identifier [Axis]: Tax Defense Network, LLC | Diversified Consumer Services 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     0    
Fair value, ending balance 0 [10],[19],[20]   0 [10],[19],[20]   0 [8],[16],[17]
Investment, Identifier [Axis]: Tecta America Corp., Construction & Engineering          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,485,000    
Fair value, ending balance 5,443,000   5,443,000   5,485,000
Investment, Identifier [Axis]: Tennenbaum Waterman Fund, LP | Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [16],[17],[24],[25]     461,000    
Fair value, ending balance 392,000 [19],[20],[26],[27]   392,000 [19],[20],[26],[27]   461,000 [16],[17],[24],[25]
Investment, Identifier [Axis]: Tennenbaum Waterman Fund, LP, Equity/Other Investments          
Schedule of Investments [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     461,000 5,802,000 5,802,000
Gross additions     0   0
Gross reductions     0   (5,020,000)
Realized Gain/(Loss)     0   0
Change in Unrealized Gain (Loss)     (69,000)   (321,000)
Fair value, ending balance 392,000   392,000   461,000
Investment, Identifier [Axis]: The E.W. Scripps Company, Media          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,658,000   2,658,000    
Investment, Identifier [Axis]: The NPD Group, LP | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: The NPD Group, LP | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     52,102,000    
Fair value, ending balance 52,102,000 [9],[10]   52,102,000 [9],[10]   52,102,000 [7],[8]
Investment, Identifier [Axis]: Therapy Brands Holdings, LLC | Health Care Technology          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 5,536,000   5,536,000    
Investment, Identifier [Axis]: Therapy Brands Holdings, LLC | Health Care Technology 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     5,565,000    
Fair value, ending balance [7],[8]         5,565,000
Investment, Identifier [Axis]: Therapy Brands Holdings, LLC | Health Care Technology 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     4,786,000    
Fair value, ending balance [7],[8]         4,786,000
Investment, Identifier [Axis]: Tivity Health, Inc. | Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     24,291,000    
Fair value, ending balance 24,167,000 [9],[10]   24,167,000 [9],[10]   24,291,000 [7],[8]
Investment, Identifier [Axis]: TransDigm, Inc., Aerospace & Defense          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,914,000    
Fair value, ending balance 3,881,000   3,881,000   3,914,000
Investment, Identifier [Axis]: Travelpro Products, Inc. | Textiles, Apparel & Luxury Goods          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[25]     183,000    
Fair value, ending balance 63,000 [10],[19],[20],[26]   63,000 [10],[19],[20],[26]   183,000 [8],[16],[17],[25]
Investment, Identifier [Axis]: Traverse Midstream Partners, LLC, Oil, Gas & Consumable Fuels          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     9,859,000    
Fair value, ending balance         9,859,000
Investment, Identifier [Axis]: Traverse Midstream Partners, LLC, Oil, Gas & Consumable Fuels 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 9,838,000   9,838,000    
Investment, Identifier [Axis]: Traverse Midstream Partners, LLC, Oil, Gas & Consumable Fuels 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 7,690,000   7,690,000    
Investment, Identifier [Axis]: Trinity Air Consultants Holdings Corp. | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 16,143,000 [10]   16,143,000 [10]   0 [8],[14]
Investment, Identifier [Axis]: Trinity Air Consultants Holdings Corp. | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Trinity Air Consultants Holdings Corp. | Professional Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     16,224,000    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   16,224,000 [8]
Investment, Identifier [Axis]: Triple Lift, Inc. | Media 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (282,000)    
Fair value, ending balance (282,000) [10],[13]   (282,000) [10],[13]   (282,000) [8],[14]
Investment, Identifier [Axis]: Triple Lift, Inc. | Media 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     36,635,000    
Fair value, ending balance 36,443,000 [9],[10],[12]   36,443,000 [9],[10],[12]   36,635,000 [7],[8],[11]
Investment, Identifier [Axis]: Triton Water Holdings, Inc., Beverages          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,402,000    
Fair value, ending balance         7,402,000
Investment, Identifier [Axis]: Truck Hero, Inc., Automobile Components 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,428,000    
Fair value, ending balance         3,428,000
Investment, Identifier [Axis]: Truck Hero, Inc., Automobile Components 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,391,000    
Fair value, ending balance         6,391,000
Investment, Identifier [Axis]: Trystar, LLC | Electrical Equipment 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     2,926,000    
Fair value, ending balance 12,552,000 [10]   12,552,000 [10]   2,926,000 [8],[14]
Investment, Identifier [Axis]: Trystar, LLC | Electrical Equipment 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Trystar, LLC | Electrical Equipment 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     24,549,000    
Fair value, ending balance 22,896,000 [9],[10],[12]   22,896,000 [9],[10],[12]   24,549,000 [7],[8],[11]
Investment, Identifier [Axis]: Trystar, LLC | Electrical Equipment 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[11]     10,364,000    
Fair value, ending balance 10,311,000 [10],[12]   10,311,000 [10],[12]   10,364,000 [8],[11]
Investment, Identifier [Axis]: UKG, Inc., Software          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     9,642,000    
Fair value, ending balance 9,012,000   9,012,000   9,642,000
Investment, Identifier [Axis]: US Anesthesia Partners, Inc., Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     6,938,000    
Fair value, ending balance 6,881,000   6,881,000   6,938,000
Investment, Identifier [Axis]: US Oral Surgery Management Holdco, LLC | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     5,050,000    
Fair value, ending balance 5,050,000 [10]   5,050,000 [10]   5,050,000 [8]
Investment, Identifier [Axis]: US Oral Surgery Management Holdco, LLC | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: US Oral Surgery Management Holdco, LLC | Health Care Providers & Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     6,997,000    
Fair value, ending balance 6,997,000 [9],[10]   6,997,000 [9],[10]   6,997,000 [7],[8]
Investment, Identifier [Axis]: US Oral Surgery Management Holdco, LLC | Health Care Providers & Services 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     6,098,000    
Fair value, ending balance 6,098,000 [9],[10]   6,098,000 [9],[10]   6,098,000 [7],[8]
Investment, Identifier [Axis]: US Oral Surgery Management Holdco, LLC | Health Care Providers & Services 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     17,668,000    
Fair value, ending balance 17,668,000 [9],[10]   17,668,000 [9],[10]   17,668,000 [7],[8]
Investment, Identifier [Axis]: US Salt Investors, LLC | Chemicals 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[26] 16,521,000   16,521,000    
Investment, Identifier [Axis]: US Salt Investors, LLC | Chemicals 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13],[26] (18,000)   (18,000)    
Investment, Identifier [Axis]: US Salt Investors, LLC | Metals & Mining 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance [8],[14]         0
Investment, Identifier [Axis]: US Salt Investors, LLC | Metals & Mining 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     25,657,000    
Fair value, ending balance [7],[8]         25,657,000
Investment, Identifier [Axis]: United Airlines, Inc., Passenger Airlines          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,722,000    
Fair value, ending balance         3,722,000
Investment, Identifier [Axis]: University Support Services, LLC , Diversified Consumer Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,882,000    
Fair value, ending balance         3,882,000
Investment, Identifier [Axis]: University Support Services, LLC, Diversified Consumer Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 4,918,000   4,918,000    
Investment, Identifier [Axis]: Univision Communications, Media          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,627,000   2,627,000    
Investment, Identifier [Axis]: Urban One, Inc. | Media          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [17]     235,000    
Fair value, ending balance 157,000 [20]   157,000 [20]   235,000 [17]
Investment, Identifier [Axis]: Urban One, Inc. | Media 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [17]     490,000    
Fair value, ending balance [17]         490,000
Investment, Identifier [Axis]: VFH Parent, LLC, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,010,000    
Fair value, ending balance 4,948,000   4,948,000   5,010,000
Investment, Identifier [Axis]: Vaco Holdings, LLC, Professional Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 447,000   447,000    
Investment, Identifier [Axis]: Vanco Payment Solutions, LLC | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (5,000)    
Fair value, ending balance 11,092,000 [10]   11,092,000 [10]   (5,000) [8],[14]
Investment, Identifier [Axis]: Vanco Payment Solutions, LLC | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (5,000)   (5,000)    
Investment, Identifier [Axis]: Vanco Payment Solutions, LLC| Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     11,147,000    
Fair value, ending balance [8]         11,147,000
Investment, Identifier [Axis]: Varicent Intermediate Holdings Corp. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 6,339,000 [10]   6,339,000 [10]   0 [8],[14]
Investment, Identifier [Axis]: Varicent Intermediate Holdings Corp. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     5,423,000    
Fair value, ending balance (21,000) [10],[13]   (21,000) [10],[13]   5,423,000 [8]
Investment, Identifier [Axis]: Varicent Intermediate Holdings Corp. | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance (35,000) [10],[13]   (35,000) [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Varicent Intermediate Holdings Corp. | Software 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance (54,000) [10],[13]   (54,000) [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Varicent Intermediate Holdings Corp. | Software 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     21,107,000    
Fair value, ending balance 21,076,000 [9],[10],[12]   21,076,000 [9],[10],[12]   21,107,000 [7],[8],[11]
Investment, Identifier [Axis]: Venture CLO 43, Ltd. 21-43A E, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     2,715,000    
Fair value, ending balance 1,724,000   1,724,000   2,715,000
Investment, Identifier [Axis]: Victors CCC Buyer, LLC | Professional Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     1,551,000    
Fair value, ending balance 2,969,000 [10]   2,969,000 [10]   1,551,000 [8]
Investment, Identifier [Axis]: Victors CCC Buyer, LLC | Professional Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 942,000 [10]   942,000 [10]   0 [8],[14]
Investment, Identifier [Axis]: Victors CCC Buyer, LLC | Professional Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     23,455,000    
Fair value, ending balance 1,543,000 [10]   1,543,000 [10]   23,455,000 [7],[8]
Investment, Identifier [Axis]: Victors CCC Buyer, LLC | Professional Services 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 0   0    
Investment, Identifier [Axis]: Victors CCC Buyer, LLC | Professional Services 5          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] 0   0    
Investment, Identifier [Axis]: Victors CCC Buyer, LLC | Professional Services 6          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 23,334,000   23,334,000    
Investment, Identifier [Axis]: Victory Buyer, LLC | Building Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     45,990,000    
Fair value, ending balance [7],[8]         45,990,000
Investment, Identifier [Axis]: Victory Buyer, LLC | Machinery          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] 37,961,000   37,961,000    
Investment, Identifier [Axis]: Victory Buyer, LLC, Building Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,375,000    
Fair value, ending balance         7,375,000
Investment, Identifier [Axis]: WCG Intermediate Corp., Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 4,414,000   4,414,000    
Investment, Identifier [Axis]: WCG Purchaser Corp., Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,479,000    
Fair value, ending balance         4,479,000
Investment, Identifier [Axis]: WHCG Purchaser III, Inc. | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     24,091,000    
Fair value, ending balance 24,712,000 [10]   24,712,000 [10]   24,091,000 [8]
Investment, Identifier [Axis]: WHCG Purchaser III, Inc. | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[30]     9,645,000    
Fair value, ending balance 10,129,000 [10],[15]   10,129,000 [10],[15]   9,645,000 [8],[30]
Investment, Identifier [Axis]: WHCG Purchaser III, Inc. | Health Care Providers & Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     0    
Fair value, ending balance 0 [10],[19],[20]   0 [10],[19],[20]   0 [8],[16],[17]
Investment, Identifier [Axis]: WIN Holdings III Corp. | Diversified Consumer Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     1,192,000    
Fair value, ending balance 3,575,000 [10],[13]   3,575,000 [10],[13]   1,192,000 [8],[14]
Investment, Identifier [Axis]: WIN Holdings III Corp. | Diversified Consumer Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     41,683,000    
Fair value, ending balance 41,683,000 [9],[10]   41,683,000 [9],[10]   41,683,000 [7],[8]
Investment, Identifier [Axis]: WIN Holdings III Corp. | Diversified Consumer Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     9,915,000    
Fair value, ending balance 9,865,000 [9],[10]   9,865,000 [9],[10]   9,915,000 [7],[8]
Investment, Identifier [Axis]: WIN Holdings III Corp. | Diversified Consumer Services 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     20,255,000    
Fair value, ending balance 20,154,000 [9],[10]   20,154,000 [9],[10]   20,255,000 [7],[8]
Investment, Identifier [Axis]: WPNT, LLC | Media          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17],[18],[22]     0    
Fair value, ending balance [8],[16],[17],[18],[22]         0
Investment, Identifier [Axis]: WPNT, LLC, Equity/Other Investments          
Schedule of Investments [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]: West Coast Dental Services, Inc. | Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     2,898,000    
Fair value, ending balance 2,901,000 [10],[13]   2,901,000 [10],[13]   2,898,000 [8],[14]
Investment, Identifier [Axis]: West Coast Dental Services, Inc. | Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     1,332,000    
Fair value, ending balance 1,325,000 [10]   1,325,000 [10]   1,332,000 [7],[8]
Investment, Identifier [Axis]: West Coast Dental Services, Inc. | Health Care Providers & Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     22,299,000    
Fair value, ending balance 22,186,000 [10]   22,186,000 [10]   22,299,000 [7],[8]
Investment, Identifier [Axis]: WestJet Loyalty, LP, Passenger Airlines          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,718,000    
Fair value, ending balance 5,485,000   5,485,000   5,718,000
Investment, Identifier [Axis]: Western Dental Holdings, LLC, Health Care Providers & Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 1,340,000   1,340,000    
Investment, Identifier [Axis]: Western Dental Holdings, LLC, Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,057,000   2,057,000    
Investment, Identifier [Axis]: Western Dental Services, Inc., Health Care Providers & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 942,000   942,000    
Investment, Identifier [Axis]: Western Dental Services, Inc., Health Care Providers & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 0   0    
Investment, Identifier [Axis]: Westwood Professional Services, Inc. | Construction & Engineering 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     4,429,000    
Fair value, ending balance 6,942,000 [10],[13]   6,942,000 [10],[13]   4,429,000 [8],[14]
Investment, Identifier [Axis]: Westwood Professional Services, Inc. | Construction & Engineering 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     0    
Fair value, ending balance 0 [10],[13]   0 [10],[13]   0 [8],[14]
Investment, Identifier [Axis]: Westwood Professional Services, Inc. | Construction & Engineering 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8],[11]     44,848,000    
Fair value, ending balance 44,621,000 [9],[10],[12]   44,621,000 [9],[10],[12]   44,848,000 [7],[8],[11]
Investment, Identifier [Axis]: Wharf Street Ratings Acquisition, LLC | Capital Markets 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (28,000)    
Fair value, ending balance (26,000) [10],[13]   (26,000) [10],[13]   (28,000) [8],[14]
Investment, Identifier [Axis]: Wharf Street Ratings Acquisition, LLC | Capital Markets 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (28,000)    
Fair value, ending balance (26,000) [10],[13]   (26,000) [10],[13]   (28,000) [8],[14]
Investment, Identifier [Axis]: Wharf Street Ratings Acquisition, LLC | Capital Markets 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     25,550,000    
Fair value, ending balance 25,440,000 [9],[10]   25,440,000 [9],[10]   25,550,000 [7],[8]
Investment, Identifier [Axis]: White Cap Supply Holdings, LLC, Building Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     5,301,000    
Fair value, ending balance 5,241,000   5,241,000   5,301,000
Investment, Identifier [Axis]: Whitehorse, Ltd. 14-1A E | Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[17],[25]     62,000    
Fair value, ending balance [8],[17],[25]         62,000
Investment, Identifier [Axis]: Wideopenwest Finance, LLC, Media          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance 2,716,000   2,716,000    
Investment, Identifier [Axis]: Wind River CLO, Ltd. 14-2A FR, Capital Markets          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     91,000    
Fair value, ending balance 100,000   100,000   91,000
Investment, Identifier [Axis]: Windsor Holdings III, LLC, Chemicals          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     3,249,000    
Fair value, ending balance 3,225,000   3,225,000   3,249,000
Investment, Identifier [Axis]: Wipfli Advisory, LLC | Financial Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (14,000)    
Fair value, ending balance 980,000 [10],[13]   980,000 [10],[13]   (14,000) [8],[14]
Investment, Identifier [Axis]: Wipfli Advisory, LLC | Financial Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[14]     (19,000)    
Fair value, ending balance (18,000) [10],[13]   (18,000) [10],[13]   (19,000) [8],[14]
Investment, Identifier [Axis]: Wipfli Advisory, LLC | Financial Services 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     16,057,000    
Fair value, ending balance 16,060,000 [9],[10]   16,060,000 [9],[10]   16,057,000 [7],[8]
Investment, Identifier [Axis]: World Business Lenders, LLC | Financial Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     1,615,000    
Fair value, ending balance 3,967,000 [10],[20]   3,967,000 [10],[20]   1,615,000 [8],[16],[17]
Investment, Identifier [Axis]: X Corp., Interactive Media & Services 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,857,000    
Fair value, ending balance         4,857,000
Investment, Identifier [Axis]: X Corp., Interactive Media & Services 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     7,468,000    
Fair value, ending balance         7,468,000
Investment, Identifier [Axis]: YummyEarth, Inc. | Food Products          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8],[16],[17]     0    
Fair value, ending balance 0 [10],[19],[20]   0 [10],[19],[20]   0 [8],[16],[17]
Investment, Identifier [Axis]: Zayo Group Holdings, Inc., Diversified Telecommunication Services          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance     4,242,000    
Fair value, ending balance 3,529,000   3,529,000   4,242,000
Investment, Identifier [Axis]: Zendesk, Inc. | Software 1          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [8]     10,462,000    
Fair value, ending balance 5,376,000 [10]   5,376,000 [10]   10,462,000 [8]
Investment, Identifier [Axis]: Zendesk, Inc. | Software 2          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, beginning balance [7],[8]     64,884,000    
Fair value, ending balance 10,243,000 [10]   10,243,000 [10]   $ 64,884,000 [7],[8]
Investment, Identifier [Axis]: Zendesk, Inc. | Software 3          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [10],[13] (105,000)   (105,000)    
Investment, Identifier [Axis]: Zendesk, Inc. | Software 4          
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]          
Fair value, ending balance [9],[10] $ 63,531,000   $ 63,531,000    
[1] Percentages are based on net assets attributable to common stock as of December 31, 2025.
[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 (as defined below).
[4] Percentages are based on net assets attributable to common stock as of June 30, 2026.
[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 (as defined below).
[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 (as defined below). 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 June 30, 2026.
[16] Non-income producing at December 31, 2025.
[17] 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, 2025, the aggregate fair value of these securities is $523.7 million or 28.5% of the Company’s net assets. The initial acquisition dates have been included for such securities.
[18] 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.”
[19] Non-income producing at June 30, 2026.
[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, 2026, the aggregate fair value of these securities is $540.2 million or 30.2% of the Company’s net assets. The initial acquisition dates have been included for such securities.
[21] 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.”
[22] Investments are held in the taxable wholly-owned, consolidated subsidiary, 54th Street Equity Holdings, Inc.
[23] Investments are held in the taxable wholly-owned, consolidated subsidiary, 54th Street Equity Holdings, Inc.
[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] 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, 2025, qualifying assets represent 92.2% of the Company's total assets.
[26] 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, 2026, qualifying assets represent 91.9% of the Company's total assets.
[27] 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.”
[28] 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.
[29] 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.
[30] The investment is on non-accrual status as of December 31, 2025.
[31] 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, 2025.
[32] 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, 2026.
[33] 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.
[34] 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.