FAIR VALUE MEASUREMENTS - Level III Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 3,728,366	$ 3,219,673	$ 3,686,956	$ 3,117,354
Purchases of investments	204,003	499,618	414,587	669,935
Proceeds from principal repayments and sales of investments	(207,470)	(288,949)	(414,261)	(362,741)
Accretion of discount/amortization of premium	3,823	4,497	8,088	7,176
Payment-in-kind	4,118	3,233	9,054	6,460
Transfers into/(out) of Level 3	0	(5,174)	43,745	(1,589)
Fair value, end of period	3,726,935	3,436,310	3,726,935	3,436,310
Net change in unrealized appreciation (depreciation) from investments still held	(5,535)	2,113	(18,180)	3,155
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	$ (5,932)	$ 3,412	$ (21,821)	$ 4,465
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)	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 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	$ 27	$ 0	$ 587	$ (4,750)
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)	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	$ 3,631,679	$ 3,093,759	$ 3,603,209	$ 2,979,870
Purchases of investments	204,003	493,351	409,348	660,813
Proceeds from principal repayments and sales of investments	(207,470)	(274,169)	(410,112)	(337,511)
Accretion of discount/amortization of premium	3,796	4,238	8,028	6,744
Payment-in-kind	3,091	2,207	7,018	4,700
Transfers into/(out) of Level 3	0	(5,174)	30,168	(1,589)
Fair value, end of period	3,630,247	3,319,052	3,630,247	3,319,052
Net change in unrealized appreciation (depreciation) from investments still held	(4,482)	3,387	(13,796)	9,438
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	(4,879)	4,840	(16,067)	10,775
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	27	0	(1,345)	(4,750)
Second Lien Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	49,212	82,186	33,351	96,848
Purchases of investments	0	0	3,064	836
Proceeds from principal repayments and sales of investments	0	(14,780)	0	(25,230)
Accretion of discount/amortization of premium	21	255	50	426
Payment-in-kind	278	230	516	365
Transfers into/(out) of Level 3	0	0	13,577	0
Fair value, end of period	49,743	67,286	49,743	67,286
Net change in unrealized appreciation (depreciation) from investments still held	232	(414)	(814)	(5,932)
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	232	(605)	(815)	(5,959)
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	0	0
Other Debt Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	9,603		9,198
Purchases of investments	0		1,021
Proceeds from principal repayments and sales of investments	0		0
Accretion of discount/amortization of premium	6		10
Payment-in-kind	267		493
Transfers into/(out) of Level 3	0		0
Fair value, end of period	9,773		9,773
Net change in unrealized appreciation (depreciation) from investments still held	(103)		(949)
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	(103)		(949)
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		0
Equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	37,872	41,565	41,198	38,572
Purchases of investments	0	497	1,154	2,516
Proceeds from principal repayments and sales of investments	0	0	(4,149)	0
Accretion of discount/amortization of premium	0	0	0	0
Payment-in-kind	482	701	1,027	1,281
Transfers into/(out) of Level 3	0	0	0	0
Fair value, end of period	37,172	41,505	37,172	41,505
Net change in unrealized appreciation (depreciation) from investments still held	(1,182)	(1,295)	(2,621)	(864)
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	(1,182)	(1,258)	(3,990)	(864)
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	$ 0	0	$ 1,932	0
Other Debt Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period		2,163		2,064
Purchases of investments		5,770		5,770
Proceeds from principal repayments and sales of investments		0		0
Accretion of discount/amortization of premium		4		6
Payment-in-kind		95		114
Transfers into/(out) of Level 3		0		0
Fair value, end of period		8,467		8,467
Net change in unrealized appreciation (depreciation) from investments still held		435		513
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		435		513
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		$ 0