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Summary of Significant Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) segment	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Related Party Transaction [Line Items]
Number of operating segments \| segment	1
Number of reportable segments \| segment	1
Excise taxes	$ 23	$ 22	$ 19
Federal income taxes paid during the year	$ 27	20	15
FS/KKR Advisor, LLC \| Investment Advisory Agreement - Incentive Rate, Realized Capital Gains
Related Party Transaction [Line Items]
Incentive fee (as percent)	20.00%
FS/KKR Advisor, LLC \| Investment Advisory Agreement - Incentive Rate, Quarterly In Arrears Catch-up Threshold
Related Party Transaction [Line Items]
Incentive fee (as percent)	17.50%
FS/KKR Advisor, LLC \| Investment Advisory Agreement - Incentive Rate, Quarterly Catch-up Threshold
Related Party Transaction [Line Items]
Incentive fee (as percent)	1.75%
FS/KKR Advisor, LLC \| Investment Advisory Agreement - Incentive Rate, Annualized Hurdle Rate
Related Party Transaction [Line Items]
Incentive fee (as percent)	7.00%
FS/KKR Advisor, LLC \| Investment Advisory Agreement - Incentive Rate, Pre-Incentive Fee Net Investment Income Below Catch-Up Threshold
Related Party Transaction [Line Items]
Incentive fee (as percent)	2.12%
FS/KKR Advisor, LLC \| Investment Advisory Agreement - Incentive Rate, Annualized Catch-Up Threshold
Related Party Transaction [Line Items]
Incentive fee (as percent)	8.48%
Structuring Fees
Related Party Transaction [Line Items]
Structuring fee revenue	$ 31	$ 20	$ 38