Investments - Schedule of Changes in Fair Value of Investments (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2025		Mar. 31, 2024
Schedule of Investments [Line Items]
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Unrealized Gain (Loss) on Investments		Unrealized Gain (Loss) on Investments
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Unrealized Gain (Loss) on Investments		Unrealized Gain (Loss) on Investments
Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		$ 2,894,850		$ 2,332,982
Net realized gains (losses)		3,413		(5,832)
Net change in unrealized gains (losses)		(5,383)		3,771
Net amortization on investments		1,687		1,939
Purchases, including capitalized PIK		391,804	[1]	155,139	[2]
Sales		(172,016)	[1]	(136,868)	[2]
Transfers out of Level 3		(6,564)	[3]	(7,710)	[4]
Fair value, Ending balance		3,107,791		2,343,421
Net change in unrealized gains (losses) on Level 3 investments still held		(4,567)		(3,938)
First Lien Secured Debt | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		2,676,253	[5]	2,075,031	[6]
Net realized gains (losses)		1,434	[5]	(6,464)	[6]
Net change in unrealized gains (losses)		(2,089)	[5]	4,581	[6]
Net amortization on investments		1,687	[5]	1,933	[6]
Purchases, including capitalized PIK		391,001	[1],[5]	154,876	[2],[6]
Sales		(164,998)	[1],[5]	(118,479)	[2],[6]
Transfers out of Level 3	[3],[5]	(6,564)
Fair value, Ending balance		2,896,724	[5]	2,111,478	[6]
Net change in unrealized gains (losses) on Level 3 investments still held		(1,528)	[5]	(3,233)	[6]
Second Lien Secured Debt | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		5,764	[5]	31,887	[6]
Net realized gains (losses)	[6]			273
Net change in unrealized gains (losses)		(1,549)	[5]	12,296	[6]
Net amortization on investments	[6]			6
Purchases, including capitalized PIK		6	[1],[5]	146	[2],[6]
Sales	[2],[6]			(31,339)
Transfers out of Level 3	[4],[6]			(7,710)
Fair value, Ending balance		4,221	[5]	5,559	[6]
Net change in unrealized gains (losses) on Level 3 investments still held		(4,533)	[5]	(594)	[6]
Unsecured Debt | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		117
Net change in unrealized gains (losses)		(8)		(2,335)
Sales	[2]			2,664
Fair value, Ending balance		109		329
Net change in unrealized gains (losses) on Level 3 investments still held		65		(2,335)
Structured Products And Other | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		26,101		41,333
Net change in unrealized gains (losses)		(431)		(3,347)
Sales		(2,178)	[1]	(2,347)	[2]
Fair value, Ending balance		23,492		35,639
Net change in unrealized gains (losses) on Level 3 investments still held		(431)		(3,346)
Preferred Equity | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		24,831		32,405
Net change in unrealized gains (losses)		(1,017)		231
Purchases, including capitalized PIK		100	[1]	116	[2]
Sales	[1]	(250)
Fair value, Ending balance		23,664		32,752
Net change in unrealized gains (losses) on Level 3 investments still held		(1,017)		231
Common Equity/Interests | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		161,648		152,127
Net realized gains (losses)		1,979		359
Net change in unrealized gains (losses)		(368)		(7,138)
Purchases, including capitalized PIK		697	[1]	1	[2]
Sales		(4,590)	[1]	12,057	[2]
Fair value, Ending balance		159,366		157,406
Net change in unrealized gains (losses) on Level 3 investments still held		2,798		5,856
Warrants - Warrants | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		136		199
Net change in unrealized gains (losses)		79		(517)
Sales	[2]			576
Fair value, Ending balance		215		258
Net change in unrealized gains (losses) on Level 3 investments still held		$ 79		$ (517)

[1] Includes reorganizations and restructuring of investments. Includes all activities from the Mergers.

[2] Includes reorganizations and restructuring of investments.

[3] Transfers out (if any) of Level 3 are due to an increase in the quantity and reliability of broker quotes obtained and transfers into (if any) Level 3 are due to a decrease in the quantity and reliability of broker quotes obtained as assessed by the Investment Adviser. Transfers are assumed to have occurred at the end of the period. There were no transfers between Level 1 and Level 2 fair value measurements during the period shown.

[4] Transfers out (if any) of Level 3 are due to an increase in the quantity and reliability of broker quotes obtained and transfers into (if any) Level 3 are due to a decrease in the quantity and reliability of broker quotes obtained as assessed by the Investment Adviser. Transfers are assumed to have occurred at the end of the period. There were no transfers between Level 1 and Level 2 fair value measurements during the period shown.

[5] Includes unfunded commitments measured at fair value of $(5,105).

[6] Includes unfunded commitments measured at fair value of (3,976).