v3.26.3
Portfolio Company Investments - Schedule of Consolidated Schedule of Investments in and Advances to Affiliates (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Schedule of Investments [Line Items]          
Fair Value, beginning balance [1],[2],[3],[4]     $ 1,324,753    
Fair Value, ending balance $ 1,435,175 [5],[6],[7],[8]   1,435,175 [5],[6],[7],[8]   $ 1,324,753 [1],[2],[3],[4]
Net realized (gain) loss on investments 10,881 $ 930 16,661 $ (4,832)  
Net Change in Unrealized Appreciation (Depreciation) 10,337 3,424 13,358 8,009  
Payment-in-kind Interest Income 3,126 $ 3,185 9,677 7,884  
Control Investments          
Schedule of Investments [Line Items]          
Principal Amount - Debt Investments 0   0   0
Gross Additions     120   5,223
Gross Reductions     (120)   (5,223)
Net realized (gain) loss on investments     (120)   (5,223)
Net Change in Unrealized Appreciation (Depreciation)         5,222
Affiliate Investments          
Schedule of Investments [Line Items]          
Principal Amount - Debt Investments 64,230   64,230   52,898
Fair Value, beginning balance     119,015 102,024 102,024
Gross Additions     39,555   41,864
Gross Reductions     (12,392)   (24,873)
Fair Value, ending balance 146,178   146,178   119,015
Net realized (gain) loss on investments     1,189   (10,963)
Net Change in Unrealized Appreciation (Depreciation)     6,799   (1,538)
Interest Income     5,081   4,619
Payment-in-kind Interest Income         0
Dividend Income     557   1,555
Fee Income     56   909
US GreenFiber, LLC | Control Investments          
Schedule of Investments [Line Items]          
Principal Amount - Debt Investments 0   0    
Gross Additions     120   5,223
Gross Reductions     (120)   (5,223)
Net realized (gain) loss on investments     (120)   (5,223)
Net Change in Unrealized Appreciation (Depreciation)         5,222
Applegate Greenfiber Intermediate Inc. (fka US GreenFiber, LLC) | Affiliate Investments          
Schedule of Investments [Line Items]          
Principal Amount - Debt Investments 9,602   9,602   9,602
Fair Value, beginning balance     26,487 24,387 24,387
Gross Additions     0   2,100
Gross Reductions     (1,607)   0
Fair Value, ending balance 24,880   24,880   26,487
Net Change in Unrealized Appreciation (Depreciation)     1,607   (2,100)
Interest Income     801   1,071
CP Communications, LLC | Affiliate Investments          
Schedule of Investments [Line Items]          
Principal Amount - Debt Investments 5,623   5,623   5,861
Fair Value, beginning balance     6,432 8,306 8,306
Gross Additions     401   125
Gross Reductions     (238)   (1,999)
Fair Value, ending balance 6,595   6,595   6,432
Net Change in Unrealized Appreciation (Depreciation)     394   (108)
Interest Income     723   1,041
Payment-in-kind Interest Income         0
Fee Income     8   20
Medsurant Holdings, LLC | Affiliate Investments          
Schedule of Investments [Line Items]          
Fair Value, beginning balance     308 9,863 9,863
Gross Additions     1,189   10,963
Gross Reductions     (1,497)   (20,518)
Fair Value, ending balance 0   0   308
Net realized (gain) loss on investments     1,189   (10,963)
Net Change in Unrealized Appreciation (Depreciation)     (307)   (6,982)
Dividend Income     0   867
Pfanstiehl, Inc | Affiliate Investments          
Schedule of Investments [Line Items]          
Fair Value, beginning balance     40,995 39,923 39,923
Gross Additions     5,829   1,072
Fair Value, ending balance 46,824   46,824   40,995
Net Change in Unrealized Appreciation (Depreciation)     5,829   1,072
Dividend Income     557   522
PIPCO, LLC | Affiliate Investments          
Schedule of Investments [Line Items]          
Principal Amount - Debt Investments 8,955   8,955   9,000
Fair Value, beginning balance     9,699    
Gross Additions     413   9,766
Gross Reductions     (44)   (67)
Fair Value, ending balance 10,068   10,068   9,699
Net Change in Unrealized Appreciation (Depreciation)     390   15
Interest Income     705   54
Fee Income     13   199
Spectra A&D Acquisition, Inc. (fka FDS Avionics Corp.) | Affiliate Investments          
Schedule of Investments [Line Items]          
Principal Amount - Debt Investments 28,435   28,435   28,435
Fair Value, beginning balance     31,197 14,921 14,921
Gross Additions     1,514   17,838
Gross Reductions         (1,562)
Fair Value, ending balance 32,711   32,711   31,197
Net Change in Unrealized Appreciation (Depreciation)     1,486   (2,877)
Interest Income     2,531   2,453
Fee Income     35   690
Steward Holding LLC (dba Steward Advanced Materials) | Affiliate Investments          
Schedule of Investments [Line Items]          
Fair Value, beginning balance     3,897 $ 4,624 4,624
Gross Additions     3,093    
Gross Reductions     (1,001)   (727)
Fair Value, ending balance 5,989   5,989   3,897
Net Change in Unrealized Appreciation (Depreciation)     3,093   (728)
Dividend Income     0   $ 166
Suited Connector LLC | Affiliate Investments          
Schedule of Investments [Line Items]          
Gross Additions     2,070    
Gross Reductions     0    
Fair Value, ending balance 2,070   2,070    
Net Change in Unrealized Appreciation (Depreciation)     (54)    
Netbase Solutions Inc | Affiliate Investments          
Schedule of Investments [Line Items]          
Principal Amount - Debt Investments 11,615   11,615    
Gross Additions     25,046    
Gross Reductions     (8,005)    
Fair Value, ending balance $ 17,041   17,041    
Net Change in Unrealized Appreciation (Depreciation)     (2,533)    
Interest Income     321    
Payment-in-kind Interest Income     $ 182    
[1]

(a) See Note 3 to the consolidated financial statements for portfolio composition by geographic location.
[2]

(b) Equity ownership may be held in shares or units of companies related to the portfolio companies. The Company’s investments are generally classified as “restricted securities”, unless otherwise noted, as such term is defined under Regulation S-X Rule 6-03(f) or Securities Act Rule 144. As of December 31, 2025, the Company held restricted securities with an aggregate fair value of $1,324,753, or 179% of the Company's net assets.
[3]

(c) All debt investments are income producing, unless otherwise indicated. Equity investments are non-income producing unless otherwise noted.
[4]

(g) Except as otherwise noted, the Company’s investment portfolio is comprised of debt and equity securities of privately held companies for which quoted prices falling within the categories of Level 1 and Level 2 inputs are not available. Therefore, the Company values all of its portfolio investments at fair value, as determined in good faith by the board of directors, using significant unobservable Level 3 inputs.
[5] All debt investments are income producing, unless otherwise indicated. Equity investments are non-income producing unless otherwise noted.
[6] Equity ownership may be held in shares or units of companies related to the portfolio companies. The Company’s investments are generally classified as “restricted securities”, unless otherwise noted, as such term is defined under Regulation S-X Rule 6-03(f) or Securities Act Rule 144. As of September 30, 2026, the Company held restricted securities with an aggregate fair value of $1,435,175, or 185% of the Company's net assets.
[7] Except as otherwise noted, the Company’s investment portfolio is comprised of debt and equity securities of privately held companies for which quoted prices falling within the categories of Level 1 and Level 2 inputs are not available. Therefore, the Company values all of its portfolio investments at fair value, as determined in good faith by the board of directors, using significant unobservable Level 3 inputs.
[8] See Note 3 to the consolidated financial statements for portfolio composition by geographic location.