FAIR VALUE MEASUREMENTS - Level III Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 3,686,956	$ 3,117,354
Purchases of investments	210,585	192,430
Proceeds from principal repayments and sales of investments	(206,792)	(95,766)
Accretion of discount/amortization of premium	4,266	2,684
Payment-in-kind	4,936	3,226
Transfers into/(out) of Level 3	43,745	3,622
Fair value, end of period	3,728,366	3,219,673
Net change in unrealized appreciation (depreciation) from investments still held	(13,259)	1,009
Net change in unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings	$ (15,892)	$ 1,748
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net change in unrealized appreciation (depreciation)	Net change in unrealized appreciation (depreciation)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net change in unrealized appreciation (depreciation)	Net change in unrealized appreciation (depreciation)
Net realized gains (losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings	$ 562	$ (5,625)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net Realized Gain (Loss)	Net Realized Gain (Loss)
First Lien Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 3,603,209	$ 2,979,870
Purchases of investments	205,347	189,612
Proceeds from principal repayments and sales of investments	(202,642)	(85,316)
Accretion of discount/amortization of premium	4,232	2,510
Payment-in-kind	3,926	2,493
Transfers into/(out) of Level 3	30,168	3,622
Fair value, end of period	3,631,679	3,093,759
Net change in unrealized appreciation (depreciation) from investments still held	(9,928)	6,024
First Lien Debt | Net change in unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings	(11,190)	6,593
First Lien Debt | Net realized gains (losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings	(1,371)	(5,625)
Second Lien Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	33,351	96,848
Purchases of investments	3,064	836
Proceeds from principal repayments and sales of investments	0	(10,450)
Accretion of discount/amortization of premium	29	172
Payment-in-kind	239	135
Transfers into/(out) of Level 3	13,577	0
Fair value, end of period	49,212	82,186
Net change in unrealized appreciation (depreciation) from investments still held	(1,046)	(5,525)
Second Lien Debt | Net change in unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings	(1,048)	(5,355)
Second Lien Debt | Net realized gains (losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings	0	0
Other Debt Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	9,198
Purchases of investments	1,021
Proceeds from principal repayments and sales of investments	0
Accretion of discount/amortization of premium	5
Payment-in-kind	226
Transfers into/(out) of Level 3	0
Fair value, end of period	9,603
Net change in unrealized appreciation (depreciation) from investments still held	(847)
Other Debt Investments | Net change in unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings	(847)
Other Debt Investments | Net realized gains (losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings	0
Equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	41,198
Purchases of investments	1,153
Proceeds from principal repayments and sales of investments	(4,150)
Accretion of discount/amortization of premium	0
Payment-in-kind	545
Transfers into/(out) of Level 3	0
Fair value, end of period	37,872
Net change in unrealized appreciation (depreciation) from investments still held	(1,438)
Equity | Net change in unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings	(2,807)
Equity | Net realized gains (losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings	$ 1,933
Other Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period		40,636
Purchases of investments		1,982
Proceeds from principal repayments and sales of investments		0
Accretion of discount/amortization of premium		2
Payment-in-kind		598
Transfers into/(out) of Level 3		0
Fair value, end of period		43,728
Net change in unrealized appreciation (depreciation) from investments still held		510
Other Securities | Net change in unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings		510
Other Securities | Net realized gains (losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings		$ 0