Fair Value of Financial Instruments - Reconciliations of Investments of Level 3 Inputs (Detail) - Level 3 - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value balance, beginning	$ 1,140,859	$ 876,843
Additions	166,572	122,907
Disposals and repayments of debt investments	(50,500)
Principal repayment	(188)	(188)
PIK interest and dividends	5,801
PIK dividends		1,490
Return of capital	(2,342)	(2,445)
Net change in unrealized appreciation, including unrealized foreign currency gain	91,888
Net change in unrealized appreciation		53,314
Fair value balance, ending	1,352,090	1,051,921
Change in net unrealized appreciation on investments held	91,888	53,314
Senior Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value balance, beginning	292,284	276,158
Additions	41,602	9,376
Disposals and repayments of debt investments	(15,000)
Principal repayment	(188)	(188)
PIK interest and dividends	913
PIK dividends		0
Return of capital	0	0
Net change in unrealized appreciation, including unrealized foreign currency gain	182
Net change in unrealized appreciation		0
Fair value balance, ending	319,793	285,346
Change in net unrealized appreciation on investments held	182	0
Equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value balance, beginning	848,575	600,685
Additions	124,970	113,531
Disposals and repayments of debt investments	(35,500)
Principal repayment	0	0
PIK interest and dividends	4,888
PIK dividends		1,490
Return of capital	(2,342)	(2,445)
Net change in unrealized appreciation, including unrealized foreign currency gain	91,706
Net change in unrealized appreciation		53,314
Fair value balance, ending	1,032,297	766,575
Change in net unrealized appreciation on investments held	$ 91,706	$ 53,314