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FAIR VALUE MEASUREMENTS - Level III Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 3,117,354	$ 2,828,035
Purchases of investments	192,430	139,034
Proceeds from principal repayments and sales of investments	(95,766)	(89,636)
Accretion of discount/amortization of premium	2,684	2,502
Payment-in-kind	3,226	1,003
Transfers into/(out) of Level 3	3,622	(16,189)
Fair value, end of period	3,219,673	2,866,154
Net change in unrealized appreciation (depreciation) from investments still held	1,009	1,285
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	$ 1,748	$ 1,283
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net change in unrealized appreciation (depreciation) on non-controlled/non-affiliated investments	Net change in unrealized appreciation (depreciation) on non-controlled/non-affiliated investments
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net change in unrealized appreciation (depreciation) on non-controlled/non-affiliated investments	Net change in unrealized appreciation (depreciation) on non-controlled/non-affiliated 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	$ (5,625)	$ 122
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gain (loss) on non-controlled/non-affiliated investments	Net realized gain (loss) on non-controlled/non-affiliated investments
First Lien Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 2,979,870	$ 2,668,749
Purchases of investments	189,612	130,460
Proceeds from principal repayments and sales of investments	(85,316)	(89,636)
Accretion of discount/amortization of premium	2,510	2,433
Payment-in-kind	2,493	382
Transfers into/(out) of Level 3	3,622	0
Fair value, end of period	3,093,759	2,713,691
Net change in unrealized appreciation (depreciation) from investments still held	6,024	1,183
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	6,593	1,181
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	(5,625)	122
Second Lien Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	96,848	122,891
Purchases of investments	836	8,500
Proceeds from principal repayments and sales of investments	(10,450)	0
Accretion of discount/amortization of premium	172	67
Payment-in-kind	135	133
Transfers into/(out) of Level 3	0	(16,189)
Fair value, end of period	82,186	115,410
Net change in unrealized appreciation (depreciation) from investments still held	(5,525)	8
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	(5,355)	8
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 Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	40,636	36,395
Purchases of investments	1,982	74
Proceeds from principal repayments and sales of investments	0	0
Accretion of discount/amortization of premium	2	2
Payment-in-kind	598	488
Transfers into/(out) of Level 3	0	0
Fair value, end of period	43,728	37,053
Net change in unrealized appreciation (depreciation) from investments still held	510	94
Other 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	510	94
Other 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

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Indicates line item in statement in which net income is reported that includes unrealized gain (loss) from asset measured at fair value using unobservable input (level 3) and still held.

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Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfers of financial instrument classified as a liability into (out of) level 3 of the fair value hierarchy.

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