Investment Portfolio - Narrative (Details) $ in Millions		3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 18, 2021 USD ($)	Jun. 30, 2023 USD ($) company	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) company	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) company	Jun. 28, 2022 USD ($)
Schedule of Investments [Line Items]
Increase in commitment							$ 440.0
Amount funded to joint venture				$ 1,799.8
Net realized gain (loss) on investments:				(272.0)	$ 151.0
Receivable for investments sold and repaid		$ 117.0		117.0		$ 212.0
FS/KKR Advisor, LLC
Schedule of Investments [Line Items]
Cost basis of investments sold				121.9
Proceeds from sale of investments				121.7
Net realized gain (loss) on investments:				(0.2)
Receivable for investments sold and repaid		$ 77.2		$ 77.2
Controlled/affiliated investments
Schedule of Investments [Line Items]
Number of investments in portfolio companies | company		18		18		18
Net realized gain (loss) on investments:		$ (172.0)	$ (39.0)	$ (172.0)	(39.0)	$ (71.4)
Non-controlled/affiliated investments
Schedule of Investments [Line Items]
Number of investments in portfolio companies | company		9		9		10
Net realized gain (loss) on investments:		$ (3.0)	$ 45.0	$ (3.0)	$ 39.0	$ 83.6
Credit Opportunities Partners JV, LLC
Schedule of Investments [Line Items]
Aggregate credit opportunities partners	$ 2,440.0
Credit opportunities partners JV, LLC, entitled to a fee percentage	0.25%
The Company
Schedule of Investments [Line Items]
Contributed capital to committed capital ratio	87.50%
Joint venture voting control, percentage	50.00%
Increase in commitment							$ 385.0
Amount funded to joint venture				1,574.8
SCRS
Schedule of Investments [Line Items]
Contributed capital to committed capital ratio	12.50%
Joint venture voting control, percentage	50.00%
Debt Securities
Schedule of Investments [Line Items]
Unfunded equity/other commitments		976.1		976.1		952.4
Unfunded Asset Based Finance/Other commitments
Schedule of Investments [Line Items]
Unfunded equity/other commitments		623.7		623.7		475.3
Credit Opportunities Partners JV, LLC | Partnership Interest
Schedule of Investments [Line Items]
Unfunded equity/other commitments		$ 560.2		$ 560.2		$ 560.2