Income Taxes - Narrative (Details) - USD ($)		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Distributions declared from earnings	[1]	$ 620,264,000	$ 507,822,000	$ 486,868,000
Tax dividend amount		620,300,000	517,900,000	484,400,000
Ordinary income		612,900,000		458,200,000
Tax on long term capital gains		7,400,000		26,200,000
Accumulated ordinary income		118,300,000	13,100,000	0
Accumulated long-term capital gain			7,400,000	0
Net change in unrealized gain (loss) on investments		(10,000,000.0)	(123,000,000.0)	(51,700,000)
Other temporary difference		$ (14,700,000)	$ 10,400,000	$ (4,700,000)
Distributed ordinary income		90.20%	85.20%	85.20%
Tax expense (benefit)		$ 12,759,000	$ 5,810,000	$ 4,009,000
Unrealized gain (loss) for U.S. federal income tax purposes		(400,000)	(126,200,000)	(36,800,000)
Cost for income tax purposes		12,700,000,000	13,100,000,000	12,800,000,000
Unrealized loss for U.S. federal income tax purposes		325,300,000	382,200,000	217,600,000
Unrealized gain for U.S. federal income tax purposes		324,900,000	256,000,000	180,800,000
Deferred tax, other				10,100,000
Other book-tax differences		12,700,000	5,800,000	4,000,000
Tax (benefit) expense for taxable subsidiaries		300,000	5,100,000	$ 4,000,000
Net deferred tax liability		$ 29,000,000	$ 16,000,000

[1] (1)For the year ended December 31, 2023 distributions declared from earnings were derived from net investment income and capital gains. For the year ended December 31, 2022, distributions declared from earnings were derived from net investment income. For the year ended December 31, 2021 distributions declared from earnings were derived from net investment income and capital gains.