Income Taxes - Schedule of Aggregate Unrealized Appreciation of Company investment Federal Income Tax (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Income Tax Disclosure [Abstract]
Aggregate gross unrealized appreciation	$ 112.0	$ 108.4
Aggregate gross unrealized depreciation	128.0	156.5
Net unrealized appreciation (depreciation) over cost for U.S. federal income tax purposes	(16.0)	(48.1)
Aggregate cost of securities for U.S. federal income tax purposes (in billions)	$ 4,200.0	$ 3,700.0