Asset-Backed Securities Issued - Accrued Interest Payable (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Amortization of debt issuance costs	$ 22,025	$ 33,686
Freddie Mac SLST
Debt Instrument [Line Items]
Amortization of debt issuance costs	5,831	5,374
Freddie Mac K-Series
Debt Instrument [Line Items]
Amortization of debt issuance costs	1,182	12,887
CAFL
Debt Instrument [Line Items]
Amortization of debt issuance costs	9,180	7,298
Asset-backed securities issued \| Legacy Sequoia
Debt Instrument [Line Items]
Amortization of debt issuance costs	180	395
Asset-backed securities issued \| Sequoia Choice
Debt Instrument [Line Items]
Amortization of debt issuance costs	$ 5,652	$ 7,732

Amount of amortization expense attributable to debt issuance costs.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(8))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

Name:	us-gaap_AmortizationOfFinancingCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration