Income Taxes - Increase in Net Assets From Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Increase (decrease) in net assets resulting from operations	$ 594,980	$ 793,312	$ 466,355
Net unrealized (gain) loss on investments	50,200	(92,900)	94,500
Other income (loss) for tax purposes, not book	12,700	(43,300)	(33,000)
Deferred organization costs	(100)	(100)	(100)
Other book-tax differences	11,600	12,700	5,800
Realized gain/loss differences	84,400	53,000	1,000
Taxable Income	$ 753,800	$ 722,700	$ 534,500