Investment Portfolio - Narrative (Details) - USD ($)		12 Months Ended
	Jun. 18, 2021	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Amount funded to joint venture		$ 1,799,800,000
Net realized gain (loss) on investments:		(486,000,000)	$ (343,000,000)	$ 149,000,000
Receivable for investments sold and repaid		186,000,000	246,000,000
Credit Opportunities Partners JV, LLC
Schedule of Investments [Line Items]
Aggregate credit opportunities partners		2,640,000,000
Cost basis of investments sold		554,100,000
Proceeds from sale of investments		559,600,000
Net realized gain (loss) on investments:		5,500,000
Credit opportunities partners JV, LLC, entitled to a fee percentage	0.25%
Receivable for investments sold and repaid		182,800,000
Administrative services		$ 9,300,000	9,300,000
FS KKR Capital Corp.
Schedule of Investments [Line Items]
Contributed capital to committed capital ratio		87.50%
Joint venture voting control, percentage		50.00%
Amount funded to joint venture		$ 1,574,800,000
SCRS
Schedule of Investments [Line Items]
Contributed capital to committed capital ratio		12.50%
Joint venture voting control, percentage		50.00%
Unfunded Dent Securities
Schedule of Investments [Line Items]
Unfunded commitments		$ 1,534,100,000	995,100,000
Unfunded Equity/Other Commitments
Schedule of Investments [Line Items]
Unfunded commitments		387,100,000	616,400,000
Partnership Interest
Schedule of Investments [Line Items]
Unfunded commitments		$ 735,200,000	$ 560,200,000
Controlled/affiliated
Schedule of Investments [Line Items]
Number of investments in portfolio companies		31	27
Net realized gain (loss) on investments:		$ 23,200,000	$ (174,800,000)	(71,000,000)
Non-controlled/affiliated
Schedule of Investments [Line Items]
Number of investments in portfolio companies		11	13
Net realized gain (loss) on investments:		$ (60,700,000)	$ (21,200,000)	$ 84,000,000