Asset-Backed Securities Issued - Accrued Interest Payable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	$ 33,686	$ 16,897
Freddie Mac SLST
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	5,374	2,907
Freddie Mac K-Series
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	12,887	6,239
CAFL
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	7,298	0
Asset-backed securities issued | Legacy Sequoia
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	395	571
Asset-backed securities issued | Sequoia Choice
Debt Instrument [Line Items]
Amortization of deferred ABS issuance costs	$ 7,732	$ 7,180