v3.26.3
INVESTMENTS - Schedule of Composition of Investment Portfolio at Cost And Fair Value (Details) - USD ($)
$ in Thousands
9 Months Ended 12 Months Ended
Sep. 30, 2026
Dec. 31, 2025
Schedule of Investments [Line Items]    
Cost $ 2,552,012 $ 2,424,280
Fair Value $ 2,509,771 $ 2,398,524
Percentage of Total Net Assets 219.50% [1] 206.60% [2]
Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Cost $ 1,284,076 $ 1,290,521
Fair Value 1,231,039 1,241,387
Thompson Rivers LLC    
Schedule of Investments [Line Items]    
Cost 62,878 118,200
Fair Value $ 54,932 111,752
Sierra JV    
Schedule of Investments [Line Items]    
Cost   2,721
Fair Value   $ 2,701
Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 100.00% 100.00%
Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 100.00% 100.00%
Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Thompson Rivers LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 100.00% 100.00%
Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Sierra JV    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio   100.00%
Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 100.00% 100.00%
Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 100.00% 100.00%
Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Thompson Rivers LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 100.00% 100.00%
Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Sierra JV    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio   100.00%
Senior debt and 1st lien notes    
Schedule of Investments [Line Items]    
Cost $ 1,820,136 $ 1,704,910
Fair Value $ 1,771,736 $ 1,676,334
Percentage of Total Net Assets 155.00% 144.00%
Senior debt and 1st lien notes | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Cost $ 1,163,544 $ 1,226,601
Fair Value $ 1,133,740 1,202,376
Senior debt and 1st lien notes | Sierra JV    
Schedule of Investments [Line Items]    
Cost   2,721
Fair Value   $ 2,701
Senior debt and 1st lien notes | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 71.00% 70.00%
Senior debt and 1st lien notes | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 91.00% 95.00%
Senior debt and 1st lien notes | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Sierra JV    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio   100.00%
Senior debt and 1st lien notes | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 71.00% 70.00%
Senior debt and 1st lien notes | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 92.00% 97.00%
Senior debt and 1st lien notes | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Sierra JV    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio   100.00%
Subordinated debt and 2nd lien notes    
Schedule of Investments [Line Items]    
Cost $ 236,083 $ 195,392
Fair Value $ 233,332 $ 190,290
Percentage of Total Net Assets 21.00% 17.00%
Subordinated debt and 2nd lien notes | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Cost $ 14,651 $ 10,561
Fair Value $ 14,931 $ 10,594
Subordinated debt and 2nd lien notes | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 9.00% 8.00%
Subordinated debt and 2nd lien notes | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 1.00% 1.00%
Subordinated debt and 2nd lien notes | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 9.00% 8.00%
Subordinated debt and 2nd lien notes | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 1.00% 1.00%
Structured products    
Schedule of Investments [Line Items]    
Cost $ 25,638 $ 39,462
Fair Value $ 23,350 $ 29,627
Percentage of Total Net Assets 2.00% 3.00%
Structured products | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 1.00% 2.00%
Structured products | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 1.00% 1.00%
Equity shares    
Schedule of Investments [Line Items]    
Cost $ 391,495 $ 382,930
Fair Value $ 444,996 $ 436,466
Percentage of Total Net Assets 39.00% 38.00%
Equity shares | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Cost $ 4,594 $ 874
Fair Value $ 5,592 362
Equity shares | Sierra JV    
Schedule of Investments [Line Items]    
Cost   0
Fair Value   $ 0
Equity shares | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 16.00% 16.00%
Equity shares | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 0.00% 0.00%
Equity shares | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Sierra JV    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio   0.00%
Equity shares | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 18.00% 18.00%
Equity shares | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 1.00% 0.00%
Equity shares | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Sierra JV    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio   0.00%
Equity warrants    
Schedule of Investments [Line Items]    
Cost $ 76 $ 76
Fair Value $ 1,369 $ 1,170
Percentage of Total Net Assets 0.00% 0.00%
Equity warrants | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 0.00% 0.00%
Equity warrants | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 0.00% 0.00%
Royalty rights    
Schedule of Investments [Line Items]    
Cost $ 1,206 $ 1,292
Fair Value $ 1,507 $ 1,486
Percentage of Total Net Assets 0.00% 0.00%
Royalty rights | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 0.00% 0.00%
Royalty rights | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 0.00% 0.00%
Investment in joint ventures    
Schedule of Investments [Line Items]    
Cost $ 77,378 $ 100,218
Fair Value $ 33,481 $ 63,151
Percentage of Total Net Assets 3.00% 5.00%
Investment in joint ventures | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Cost $ 27,612 $ 34,704
Fair Value $ 3,101 $ 10,274
Investment in joint ventures | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 3.00% 4.00%
Investment in joint ventures | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 2.00% 3.00%
Investment in joint ventures | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 1.00% 3.00%
Investment in joint ventures | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 0.00% 1.00%
Short-term investments | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Cost $ 73,675 $ 17,781
Fair Value $ 73,675 $ 17,781
Short-term investments | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 6.00% 1.00%
Short-term investments | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Jocassee Partners LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 6.00% 1.00%
Federal Housing Administration (“FHA”) loans | Thompson Rivers LLC    
Schedule of Investments [Line Items]    
Cost $ 60,765 $ 112,317
Fair Value $ 53,095 $ 106,195
Federal Housing Administration (“FHA”) loans | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Thompson Rivers LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 97.00% 95.00%
Federal Housing Administration (“FHA”) loans | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Thompson Rivers LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 97.00% 95.00%
Veterans Affairs (“VA”) loans | Thompson Rivers LLC    
Schedule of Investments [Line Items]    
Cost $ 2,113 $ 5,883
Fair Value $ 1,837 $ 5,557
Veterans Affairs (“VA”) loans | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk | Thompson Rivers LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 3.00% 5.00%
Veterans Affairs (“VA”) loans | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk | Thompson Rivers LLC    
Schedule of Investments [Line Items]    
Percentage of Total Portfolio 3.00% 5.00%
[1] Fair value as a percentage of net assets.
[2] Fair value as a percentage of net assets.