INVESTMENTS - Investment Portfolio at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	$ 4,033,847	$ 3,094,065
Senior debt and 1st lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	3,362,566	2,503,156
Subordinated debt and 2nd lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	176,250	122,748
Structured products
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	98,777	80,401
Equity shares
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	371,196	337,684
Equity warrants
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	1,084	2,813
Royalty rights
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	3,854	14,583
Short-term investments
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	10,588	10,200
Level 1
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	10,588	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	10,588	10,200
Level 2
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	371,283	173,320
Level 2 | Senior debt and 1st lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	259,072	100,979
Level 2 | Subordinated debt and 2nd lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	27,818	11,839
Level 2 | Structured products
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	84,393	60,502
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	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	3,642,444	2,888,065
Level 3 | Senior debt and 1st lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	3,103,494	2,402,177
Level 3 | Subordinated debt and 2nd lien notes
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	148,432	110,909
Level 3 | Structured products
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	14,384	19,899
Level 3 | Equity shares
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	371,196	337,684
Level 3 | Equity warrants
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	1,084	2,813
Level 3 | Royalty rights
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	3,854	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	4,024,315	3,071,585
Investments in joint ventures
Schedule of Equity Method Investments [Line Items]
Total investments at fair value	$ 9,532	$ 22,480