Investments - Schedule of Changes in Fair Value of Investments (Detail) - USD ($) $ in Thousands		9 Months Ended		12 Months Ended
		Dec. 31, 2022		Dec. 31, 2023
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		$ 2,521,943		$ 2,396,036
Net realized gains (losses)		(69,512)		7,469
Net change in unrealized gains (losses)		13,101		5,380
Net amortization on investments		14,754		7,790
Purchases, including capitalized PIK		641,805	[1]	575,914	[2]
Sales		(725,703)	[1]	(660,202)	[2]
Transfers out of Level 3	[3]	(352)
Transfers into Level 3	[4]			595
Fair value, Ending balance		2,396,036		2,332,982
Net change in unrealized gains (losses) on Level 3 investments still held		(57,714)		6,375
First Lien Secured Debt | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance	[5]	2,259,506		2,130,309	[6]
Net realized gains (losses)		(791)	[5]	8,066	[6]
Net change in unrealized gains (losses)		(18,690)	[5]	1,808	[6]
Net amortization on investments		11,881	[5]	7,536	[6]
Purchases, including capitalized PIK		501,950	[1],[5]	521,876	[2],[6]
Sales		(625,264)	[1],[5]	(594,564)	[2],[6]
Transfers out of Level 3	[3],[5]	1,717
Fair value, Ending balance	[6]	2,130,309	[5]	2,075,031
Net change in unrealized gains (losses) on Level 3 investments still held		(17,540)	[5]	334	[6]
Second Lien Secured Debt | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance	[5]	97,844		70,919	[6]
Net realized gains (losses)		(27)	[5]	(978)	[6]
Net change in unrealized gains (losses)		(16,582)	[5]	20,424	[6]
Net amortization on investments		2,873	[5]	254	[6]
Purchases, including capitalized PIK		204	[1],[5]	138	[2],[6]
Sales		(11,676)	[1],[5]	(58,870)	[2],[6]
Transfers out of Level 3	[3],[5]	(1,717)
Fair value, Ending balance	[6]	70,919	[5]	31,887
Net change in unrealized gains (losses) on Level 3 investments still held		(17,835)	[5]	(1,613)	[6]
Unsecured Debt | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance				50
Purchases, including capitalized PIK		50	[1]	2	[2]
Sales	[2]			(52)
Fair value, Ending balance		50
Structured Products And Other | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		10,038		9,413
Net change in unrealized gains (losses)		(625)		3,924
Purchases, including capitalized PIK	[2]			30,077
Sales	[2]			(2,081)
Fair value, Ending balance		9,413		41,333
Net change in unrealized gains (losses) on Level 3 investments still held		(625)		4,977
Preferred Equity | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		30,162		35,557
Net change in unrealized gains (losses)		6,164		11,692
Purchases, including capitalized PIK		1,280	[1]	67	[2]
Sales		(2,049)	[1]	(14,911)	[2]
Fair value, Ending balance		35,557		32,405
Net change in unrealized gains (losses) on Level 3 investments still held		9,103		(1,258)
Common Equity/Interests | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		124,294		149,314
Net realized gains (losses)		(68,694)		381
Net change in unrealized gains (losses)		42,713		(32,193)
Purchases, including capitalized PIK		138,067	[1]	23,754	[2]
Sales		(86,714)	[1]	10,276	[2]
Transfers out of Level 3	[3]	(352)
Transfers into Level 3	[4]			595
Fair value, Ending balance		149,314		152,127
Net change in unrealized gains (losses) on Level 3 investments still held		(30,939)		4,209
Warrants - Warrants | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		99		474
Net change in unrealized gains (losses)		121		(275)
Purchases, including capitalized PIK	[1]	254
Fair value, Ending balance		474		199
Net change in unrealized gains (losses) on Level 3 investments still held		$ 122		$ (274)

[1] Includes reorganizations and restructuring of investments.

[2] Includes reorganizations and restructuring of investments.

[3] Transfers out of Level 3 are due to an increase in the quantity and reliability of broker quotes obtained and transfers into 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 of Level 3 are due to an increase in the quantity and reliability of broker quotes obtained and transfers into 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 $(2,479).

[6] Includes unfunded commitments measured at fair value of $(3,602).