Investments - Schedule of Changes in Fair Value of Investments (Detail) - Level 3 - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2025		Jun. 30, 2024		Jun. 30, 2025		Jun. 30, 2024
Schedule of Investments [Line Items]
Fair value, Beginning balance		$ 3,107,791		$ 2,343,421		$ 2,894,850		$ 2,332,982
Net realized gains (losses)		(14,727)		(12,529)		(11,322)		(17,855)
Net change in unrealized gains (losses)		724		8,429		(4,667)		12,200
Net amortization on investments		1,555		1,642		3,291		3,580
Purchases, including capitalized PIK		293,928	[1]	248,567		685,470	[2]	471,053	[3]
Sales		(139,382)	[1]	(154,878)		(311,370)	[2]	(359,598)	[3]
Transfers out of Level 3		(270)	[4]			(6,633)	[5]	(7,710)	[6]
Fair value, Ending balance		3,249,619		2,434,652		3,249,619		2,434,652
Net change in unrealized gains (losses) on Level 3 investments still held		(12,547)		(8,188)		(14,703)		(12,293)
First Lien Secured Debt
Schedule of Investments [Line Items]
Fair value, Beginning balance		2,896,724	[7]	2,111,478		2,676,253	[8]	2,075,031	[9]
Net realized gains (losses)		(9,558)	[7]	3,171		(8,132)	[8]	(2,787)	[9]
Net change in unrealized gains (losses)		(3,715)	[7]	(5,288)		(5,813)	[8]	(707)	[9]
Net amortization on investments		1,555	[7]	1,642		3,291	[8]	3,574	[9]
Purchases, including capitalized PIK		288,749	[1],[7]	245,797		679,489	[2],[8]	468,019	[3],[9]
Sales		(137,670)	[1],[7]	(153,987)		(302,640)	[2],[8]	(340,317)	[3],[9]
Transfers out of Level 3		(270)	[4],[7]			(6,633)	[5],[8]
Fair value, Ending balance		3,035,815	[7],[8]	2,202,813	[9]	3,035,815	[7],[8]	2,202,813	[9]
Net change in unrealized gains (losses) on Level 3 investments still held		(11,672)	[7]	(6,256)		(11,490)	[8]	(9,558)	[9]
Second Lien Secured Debt
Schedule of Investments [Line Items]
Fair value, Beginning balance		4,221	[7]	5,559		5,764	[8]	31,887	[9]
Net realized gains (losses)		(2,501)	[7]			(2,501)	[8]	273	[9]
Net change in unrealized gains (losses)		(1,167)	[7]	(265)		(2,716)	[8]	12,031	[9]
Net amortization on investments	[9]							6
Purchases, including capitalized PIK		3	[1],[7]	152		9	[2],[8]	299	[3],[9]
Sales		(481)	[1],[7]			(481)	[2],[8]	(31,340)	[3],[9]
Transfers out of Level 3	[9]							(7,710)
Fair value, Ending balance		75	[7],[8]	5,446	[9]	75	[7],[8]	5,446	[9]
Net change in unrealized gains (losses) on Level 3 investments still held		(3,927)	[7]	(228)		(7,705)	[8]	(858)	[9]
Unsecured Debt
Schedule of Investments [Line Items]
Fair value, Beginning balance		109		329		117
Net realized gains (losses)		(2,672)	[7]			(2,672)
Net change in unrealized gains (losses)		2,584		(12)		2,576		(2,347)
Purchases, including capitalized PIK				8				8	[3],[9]
Sales	[3]							2,664
Fair value, Ending balance		21		325		21		325
Net change in unrealized gains (losses) on Level 3 investments still held		0		42		0		(2,347)
Structured Products And Other
Schedule of Investments [Line Items]
Fair value, Beginning balance		23,492		35,639		26,101		41,333
Net change in unrealized gains (losses)		(1,025)		(2,725)		(1,456)		(6,072)
Purchases, including capitalized PIK		152	[1]	2,533		152	[2]	2,533	[3],[9]
Sales		(1,020)	[1]	(742)		(3,198)	[2]	(3,089)	[3]
Fair value, Ending balance		21,599		34,705		21,599		34,705
Net change in unrealized gains (losses) on Level 3 investments still held		(1,025)		(2,725)		(1,456)		(6,072)
Preferred Equity
Schedule of Investments [Line Items]
Fair value, Beginning balance		23,664		32,752		24,831		32,405
Net change in unrealized gains (losses)		(4,218)		(142)		(5,235)		89
Purchases, including capitalized PIK		4,449	[1]			4,549	[2]	116	[3]
Sales	[2]					(250)
Fair value, Ending balance		23,895		32,610		23,895		32,610
Net change in unrealized gains (losses) on Level 3 investments still held		(4,215)		(142)		(5,235)		89
Common Equity/Interests
Schedule of Investments [Line Items]
Fair value, Beginning balance		159,366		157,406		161,648		152,127
Net realized gains (losses)		4		(15,700)		1,983		(15,341)
Net change in unrealized gains (losses)		8,318		16,949		7,951		9,811
Purchases, including capitalized PIK		575	[1]	77		1,271	[2]	78	[3]
Sales		(211)	[1]	(149)		(4,801)	[2]	11,908	[3]
Fair value, Ending balance		168,052		158,583		168,052		158,583
Net change in unrealized gains (losses) on Level 3 investments still held		8,345		1,208		11,157		7,058
Warrants - Warrants
Schedule of Investments [Line Items]
Fair value, Beginning balance		215		258		136		199
Net change in unrealized gains (losses)		(53)		(88)		26		(605)
Sales	[3]							576
Fair value, Ending balance		162		170		162		170
Net change in unrealized gains (losses) on Level 3 investments still held		$ (54)		$ (87)		$ 26		$ (605)

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

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

[3] Includes reorganizations and restructuring of investments.

[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] 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.

[6] 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.

[7] Includes unfunded commitments measured at fair value of $(7,018).

[8] Includes unfunded commitments measured at fair value of $(7,018).

[9] Includes unfunded commitments measured at fair value of $(4,072).