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Related Party Transactions - Narrative (Details) - USD ($) $ in Millions				12 Months Ended
	Jun. 15, 2019	Jun. 14, 2019	Dec. 20, 2018	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Asset coverage per ratio (as percent)				177.00%	190.00%	183.00%	180.00%	184.00%
Investment Advisory Agreement | FS/KKR Advisor, LLC
Related Party Transaction [Line Items]
Management and service fees, base rate (as percent)	1.00%	1.50%	1.50%
Asset coverage per ratio (as percent)	150.00%	200.00%
Affiliated Purchaser Program | FS/KKR Advisor, LLC
Related Party Transaction [Line Items]
Commitment to investment vehicle				$ 100
Investment vehicle				$ 350

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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