Related Party Transactions - Narrative (Details) $ in Millions					3 Months Ended		21 Months Ended
		Jun. 15, 2019	Jun. 14, 2019	Dec. 20, 2018	Mar. 31, 2023 USD ($) qtr	Mar. 31, 2022 USD ($)	Mar. 31, 2023 USD ($) qtr	Dec. 31, 2022
Related Party Transaction [Line Items]
Asset coverage per ratio					180.00%		180.00%	180.00%
Incentive fees waived	[1]				$ 0	$ 15
FS/KKR Advisor, LLC | Investment Advisory Agreement
Related Party Transaction [Line Items]
Management and service fees, base rate		1.00%	1.50%	1.50%
Asset coverage per ratio		150.00%	200.00%
Incentive fee (in percent)		17.50%	20.00%		20.00%
Investment company, preceding calendar quarterly | qtr					11		6
Incentive fees waived quarterly							$ 15
Incentive fees waived							90
FS/KKR Advisor, LLC | Affiliated Purchaser Program
Related Party Transaction [Line Items]
Commitment to investment vehicle						$ 100
Investment vehicle					$ 350		$ 350

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