Asset-Backed Securities Issued - Accrued Interest Payable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	$ 21,793	$ 33,686
Freddie Mac SLST
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	5,656	5,374
Freddie Mac K-Series
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	1,177	12,887
CAFL
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	10,122	7,298
Asset-backed securities issued | Legacy Sequoia
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	141	395
Asset-backed securities issued | Sequoia Choice
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	$ 4,697	$ 7,732