Related Party Transactions - Fees And Expenses Accrued Under The Investment Advisory Agreement (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Related Party Transaction [Line Items]
Base Management Fee		$ 56.0	$ 63.0	$ 114.0	$ 125.0
Subordinated Incentive Fee on Income	[1]	47.0	37.0	93.0	77.0
Administrative Services Expenses		1.0	1.0	2.0	2.0
Management fees payable		56.0		56.0		$ 59.0
Incentive fee payable	[2]	47.0		47.0		$ 27.0
FS/KKR Advisor, LLC
Related Party Transaction [Line Items]
Base Management Fee		56.0	63.0	114.0	125.0
Subordinated Incentive Fee on Income		47.0	22.0	93.0	47.0
Administrative Services Expenses		4.0	$ 4.0	7.0	8.0
Base management fees				117.0	122.0
Management fees payable		56.0		56.0
Incentive fee waiver					30.0
Incentive fee paid				73.0	44.0
Incentive fee payable		$ 47.0		47.0
Allocation of costs of administrative personnel for services rendered				6.0	7.0
Broken deal cost				0.3
Payment for administrative services expenses				$ 7.0	$ 8.0

[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.