Investments - Investment Portfolio at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	$ 3,094,065	$ 2,458,929
Senior debt and 1st lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	2,503,156	1,958,306
Subordinated debt and 2nd lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	122,748	148,450
Structured Product
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	80,401	23,947
Equity shares
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	337,684	297,213
Equity warrants
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	2,813	2,475
Royalty rights
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	14,583
Short-term investments
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	10,200	0
Level 1
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	10,200	75
Level 1 | Senior debt and 1st lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0	0
Level 1 | Subordinated debt and 2nd lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0	0
Level 1 | Structured Product
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0	0
Level 1 | Equity shares
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0	75
Level 1 | Equity warrants
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0	0
Level 1 | Royalty rights
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0
Level 1 | Short-term investments
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	10,200
Level 2
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	173,320	69,092
Level 2 | Senior debt and 1st lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	100,979	42,673
Level 2 | Subordinated debt and 2nd lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	11,839	18,177
Level 2 | Structured Product
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	60,502	8,242
Level 2 | Equity shares
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0	0
Level 2 | Equity warrants
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0	0
Level 2 | Royalty rights
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0
Level 2 | Short-term investments
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0
Level 3
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	2,888,065	2,361,224
Level 3 | Senior debt and 1st lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	2,402,177	1,915,633
Level 3 | Subordinated debt and 2nd lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	110,909	130,273
Level 3 | Structured Product
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	19,899	15,705
Level 3 | Equity shares
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	337,684	297,138
Level 3 | Equity warrants
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	2,813	2,475
Level 3 | Royalty rights
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	14,583
Level 3 | Short-term investments
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0
Investments subject to leveling
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	3,071,585	2,430,391
Investment in joint ventures
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	$ 22,480	$ 28,538