Investments - Schedule of Changes in Fair Value of Investments (Detail) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2024		Jun. 30, 2023		Jun. 30, 2024		Jun. 30, 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		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		Unrealized Gain (Loss) on Investments		Unrealized Gain (Loss) on Investments
Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		$ 2,343,421		$ 2,383,518		$ 2,332,982		$ 2,396,036
Net realized gains (losses)		(12,529)		448		(17,855)		2,219
Net change in unrealized gains (losses)		8,429		(1,901)		12,200		993
Net amortization on investments		1,642		2,090		3,580		4,587
Purchases, including capitalized PIK		248,567	[1]	238,672	[2]	471,053	[1]	413,809	[2]
Sales		(154,878)	[1]	(215,492)	[2]	(359,598)	[1]	(410,309)	[2]
Transfers out of Level 3	[3]					(7,710)
Transfers into Level 3	[4]			592				592
Fair value, Ending balance		2,434,652		2,407,927		2,434,652		2,407,927
Net change in unrealized gains (losses) on Level 3 investments still held		(8,188)		(1,827)		(12,293)		1,006
First Lien Secured Debt | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		2,111,478	[5]	2,114,795	[6]	2,075,031	[5]	2,130,309	[6]
Net realized gains (losses)		3,171	[5]	448	[6]	(2,787)	[5]	2,980	[6]
Net change in unrealized gains (losses)		(5,288)		2,381	[6]	(707)	[5]	2,653	[6]
Net amortization on investments		1,642		2,041	[6]	3,574	[5]	4,463	[6]
Purchases, including capitalized PIK		245,797	[1],[5]	208,572	[2],[6]	468,019	[1],[5]	360,080	[2],[6]
Sales		(153,987)	[1],[5]	(211,871)	[2],[6]	(340,317)	[1],[5]	(384,119)	[2],[6]
Fair value, Ending balance		2,202,813	[5]	2,116,366	[6]	2,202,813	[5]	2,116,366	[6]
Net change in unrealized gains (losses) on Level 3 investments still held		(6,256)	[5]	899	[6]	(9,558)	[5]	1,342	[6]
Second Lien Secured Debt | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		5,559	[5]	69,357	[6]	31,887	[5]	70,919	[6]
Net realized gains (losses)						273	[5]	(1,128)	[6]
Net change in unrealized gains (losses)		(265)		(967)	[6]	12,031	[5]	21,016	[6]
Net amortization on investments				49	[6]	6	[5]	160	[6]
Purchases, including capitalized PIK	[1],[5]	152				299
Sales						(31,340)	[1],[5]	(22,528)	[2],[6]
Transfers out of Level 3	[3],[5]					(7,710)
Fair value, Ending balance		5,446	[5]	68,439	[6]	5,446	[5]	68,439	[6]
Net change in unrealized gains (losses) on Level 3 investments still held		(228)	[5]	(965)	[6]	(858)	[5]	(1,200)	[6]
Unsecured Debt | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		329		31				50
Net change in unrealized gains (losses)		(12)				(2,347)		(2)
Purchases, including capitalized PIK		8	[1],[5]	1	[2]	8	[1],[5]	2	[2]
Sales				(6)	[2]	2,664	[1]	(24)	[2]
Fair value, Ending balance		325		26		325		26
Net change in unrealized gains (losses) on Level 3 investments still held		42				(2,347)		(2)
Structured Products And Other | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		35,639		10,902		41,333		9,413
Net change in unrealized gains (losses)		(2,725)		(412)		(6,072)		972
Purchases, including capitalized PIK		2,533	[1]	29,947	[2]	2,533	[1]	30,052	[2]
Sales	[1]	(742)				(3,089)
Fair value, Ending balance		34,705		40,437		34,705		40,437
Net change in unrealized gains (losses) on Level 3 investments still held		(2,725)		872		(6,072)		2,025
Preferred Equity | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		32,752		36,611		32,405		35,557
Net change in unrealized gains (losses)		(142)		(226)		89		778
Purchases, including capitalized PIK						116	[1]	50	[2]
Fair value, Ending balance		32,610		36,385		32,610		36,385
Net change in unrealized gains (losses) on Level 3 investments still held		(142)		(227)		89		777
Common Equity/Interests | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		157,406		151,361		152,127		149,314
Net realized gains (losses)		(15,700)				(15,341)		367
Net change in unrealized gains (losses)		16,949		(2,553)		9,811		(24,287)
Net amortization on investments								(36)
Purchases, including capitalized PIK		77	[1]	152	[2]	78	[1]	23,625	[2]
Sales		(149)	[1]	(3,615)	[2]	11,908	[1]	(3,638)	[2]
Transfers into Level 3	[4]			592				592
Fair value, Ending balance		158,583		145,937		158,583		145,937
Net change in unrealized gains (losses) on Level 3 investments still held		1,208		(2,283)		7,058		(1,799)
Warrants - Warrants | Level 3
Schedule of Investments [Line Items]
Fair value, Beginning balance		258		461		199		474
Net change in unrealized gains (losses)		(88)		(124)		(605)		(137)
Sales	[1]					576
Fair value, Ending balance		170		337		170		337
Net change in unrealized gains (losses) on Level 3 investments still held		$ (87)		$ (123)		$ (605)		$ (137)

[1] Includes reorganizations and restructuring of investments

[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 $(4,072).

[6] Includes unfunded commitments measured at fair value of $(4,137).