Financial Highlights - Schedule of Information about Senior Securities Parenthetical (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Jul. 28, 2023	Dec. 31, 2022	Dec. 31, 2021	Oct. 27, 2021	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 29, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 29, 2015
Investment Company, Financial Highlights [Line Items]
Asset coverage per unit	$ 1,000
Revolving Credit Facility
Investment Company, Financial Highlights [Line Items]
Asset coverage per unit										$ 2,347	$ 2,415	$ 50,000
Revolving Credit Facility With Capital One
Investment Company, Financial Highlights [Line Items]
Asset coverage per unit									$ 75,000
Ally Corporate Revolving Facility
Investment Company, Financial Highlights [Line Items]
Asset coverage per unit					$ 200,000		$ 2,166	$ 2,250
FCRX Unsecured Notes
Investment Company, Financial Highlights [Line Items]
Asset coverage per unit	1,860
Amount of indebtedness used to express average market price per unit	$ 1,000
Series 2020A Notes
Investment Company, Financial Highlights [Line Items]
Asset coverage per unit		$ 50,000	$ 1,917	$ 2,014			2,166
InterNotes
Investment Company, Financial Highlights [Line Items]
Asset coverage per unit						$ 16,400	$ 2,166