INVESTMENTS - Investment Portfolio at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	$ 4,479,835	$ 3,094,065
Senior debt and 1st lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	3,798,999	2,503,156
Subordinated debt and 2nd lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	187,919	122,748
Structured products
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	103,020	80,401
Equity shares
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	366,880	337,684
Equity warrants
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	1,065	2,813
Royalty rights
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	3,953	14,583
Short-term investments
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	10,702	10,200
Level 1
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	10,702	10,200
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 products
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	0
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	0
Level 1 | Short-term investments
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	10,702	10,200
Level 2
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	440,309	173,320
Level 2 | Senior debt and 1st lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	320,497	100,979
Level 2 | Subordinated debt and 2nd lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	26,815	11,839
Level 2 | Structured products
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	89,255	60,502
Level 2 | Equity shares
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	3,742	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	0
Level 2 | Short-term investments
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0	0
Level 3
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	4,021,527	2,888,065
Level 3 | Senior debt and 1st lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	3,478,502	2,402,177
Level 3 | Subordinated debt and 2nd lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	161,104	110,909
Level 3 | Structured products
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	13,765	19,899
Level 3 | Equity shares
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	363,138	337,684
Level 3 | Equity warrants
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	1,065	2,813
Level 3 | Royalty rights
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	3,953	14,583
Level 3 | Short-term investments
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	0	0
Investments subject to leveling
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	4,472,538	3,071,585
Investments in joint ventures
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	$ 7,297	$ 22,480