Secured Borrowings- Collateralized Loan Obligations (Details) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Aug. 31, 2019 USD ($)	Mar. 31, 2021 USD ($) item	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) item
Summary of CLO
Carrying value		$ 931,178		$ 930,554
LIBOR | Collateral assets
Summary of CLO
Spread (as a percent)		4.21%		3.93%
LIBOR | Financing
Summary of CLO
Spread (as a percent)		1.63%		1.64%
Collateralized Loan Obligation
Summary of CLO
Amount issued	$ 1,100,000
Principal Amount	86,600
Liquidation preference	77,000
Incurred debt issuance costs	9,200
Amortization of deferred financing costs		$ 600	$ 600
Deferred financing costs, net of amortization		5,200		$ 5,800
Principal amount of notes purchased by third-party investors	$ 936,400
Additional Contribution to CLO		$ 98,600
Collateralized Loan Obligation | Collateral assets
Summary of CLO
Count | item		25		23
Amount issued		$ 1,099,693		$ 1,002,445
Carrying value		$ 1,099,639		$ 1,099,439
Collateralized Loan Obligation | Financing
Summary of CLO
Count | item		1		1
Amount issued		$ 936,375		$ 936,375
Carrying value		$ 931,178		$ 930,554