Related Party Transactions - Fees And Expenses Accrued Under The Investment Advisory Agreement (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Related Party Transaction [Line Items]
Base Management Fee		$ 58.0	$ 62.0
Subordinated Incentive Fee on Income	[1]	46.0	40.0
Administrative Services Expenses		1.0	1.0
Management fees payable		58.0		$ 59.0
Incentive fee payable	[2]	46.0		$ 27.0
FS/KKR Advisor, LLC
Related Party Transaction [Line Items]
Base Management Fee		58.0	62.0
Subordinated Incentive Fee on Income		46.0	25.0
Administrative Services Expenses		3.0	4.0
Base management fees		59.0	60.0
Management fees payable		58.0
Incentive fee waiver			15.0
Incentive fee paid		27.0	19.0
Incentive fee payable		46.0
Allocation of costs of administrative personnel for services rendered		3.0	4.0
Broken deal cost		0.3
Payment for administrative services expenses		$ 2.0	$ 2.0

[1] See Note 2 and 4 for a discussion of the methodology employed by the Company in calculating the subordinated income incentive fees.

[2] See Note 2 and 4 for a discussion of the methodology employed by the Company in calculating the subordinated income incentive fees.