FAIR VALUE MEASUREMENTS - Schedule of Reconciliation of the Beginning and Ending Balances for Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Total
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 1,911,267	$ 1,332,959	$ 1,598,514	$ 1,177,412
Purchase of investments	201,619	150,845	655,865	352,771
Proceeds from principal repayments and sales of investments	(125,011)	(17,424)	(267,474)	(62,619)
Payment-in-kind interest	2,503	951	6,024	1,823
Amortization of premium/accretion of discount, net	827	455	538	1,956
Transfers out of level 3	(17,813)	(17,900)	(11,899)	(22,489)
Transfers to level 3	16,525		19,500	8,348
Ending balance	1,994,851	1,448,569	1,994,851	1,448,569
Net change in unrealized appreciation (depreciation) on non-controlled/non-affiliated company investments still held	4,502	(338)	(9,815)	(2,645)
First-Lien Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	1,724,399	1,152,917	1,393,011	1,016,856
Purchase of investments	185,445	126,344	626,552	290,203
Proceeds from principal repayments and sales of investments	(120,908)	(17,172)	(244,709)	(41,652)
Payment-in-kind interest	172	0	580	0
Amortization of premium/accretion of discount, net	708	373	118	1,642
Transfers out of level 3	(17,813)	(9,540)	(11,899)	(14,042)
Transfers to level 3	16,525		19,500	8,348
Ending balance	1,791,571	1,254,096	1,791,571	1,254,096
Net change in unrealized appreciation (depreciation) on non-controlled/non-affiliated company investments still held	2,661	2,153	5,370	(1,035)
Subordinated Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	154,692	155,148	174,696	133,243
Purchase of investments	14,802	19,437	24,953	54,688
Proceeds from principal repayments and sales of investments	(4,103)	(252)	(22,692)	(12,300)
Payment-in-kind interest	2,331	951	5,444	1,823
Amortization of premium/accretion of discount, net	119	82	420	314
Transfers out of level 3	0	(8,360)	0	(8,447)
Transfers to level 3	0		0	0
Ending balance	169,455	166,458	169,455	166,458
Net change in unrealized appreciation (depreciation) on non-controlled/non-affiliated company investments still held	1,564	(548)	(13,916)	(3,036)
Equity Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	32,176	24,894	30,807	27,313
Purchase of investments	1,372	5,064	4,360	7,880
Proceeds from principal repayments and sales of investments	0	0	(73)	(8,667)
Payment-in-kind interest	0	0	0	0
Amortization of premium/accretion of discount, net	0	0	0	0
Transfers out of level 3	0	0	0	0
Transfers to level 3	0		0	0
Ending balance	33,825	28,015	33,825	28,015
Net change in unrealized appreciation (depreciation) on non-controlled/non-affiliated company investments still held	277	(1,943)	(1,269)	1,426
Net realized gain (loss) on investments | Total
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains (losses) included in earnings	913	(13,152)	(1,801)	(6,454)
Net realized gain (loss) on investments | First-Lien Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains (losses) included in earnings	810	(13,153)	(2,176)	(12,762)
Net realized gain (loss) on investments | Subordinated Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains (losses) included in earnings	103	1	375	197
Net realized gain (loss) on investments | Equity Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains (losses) included in earnings	0	0	0	6,111
Net change in unrealized appreciation (depreciation) on investments | Total
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains (losses) included in earnings	4,021	11,835	(4,416)	(2,179)
Net change in unrealized appreciation (depreciation) on investments | First-Lien Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains (losses) included in earnings	2,233	14,327	10,594	5,503
Net change in unrealized appreciation (depreciation) on investments | Subordinated Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains (losses) included in earnings	1,511	(549)	(13,741)	(3,060)
Net change in unrealized appreciation (depreciation) on investments | Equity Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains (losses) included in earnings	$ 277	$ (1,943)	$ (1,269)	$ (4,622)