Asset-Backed Securities Issued - Components of Asset-Backed Securities Issued by Consolidated Securitization Entities Sponsored, Along With Other Selected Information (Details) - Asset-backed securities issued $ in Thousands	Jun. 30, 2020 USD ($) series	Dec. 31, 2019 USD ($) series
Debt Instrument [Line Items]
Long-term debt	$ 6,856,086	$ 10,515,475
Revision of Prior Period, Accounting Standards Update, Adjustment
Debt Instrument [Line Items]
Long-term debt	32,859	197,110
Certificates with principal balance
Debt Instrument [Line Items]
Certificates	6,679,180	9,962,253
Interest-only certificates
Debt Instrument [Line Items]
Certificates	144,047	356,112
Legacy Sequoia
Debt Instrument [Line Items]
Long-term debt	$ 300,357	$ 402,465
Number of series | series	20	20
Legacy Sequoia | Revision of Prior Period, Accounting Standards Update, Adjustment
Debt Instrument [Line Items]
Long-term debt	$ (79,140)	$ (18,873)
Legacy Sequoia | Minimum
Debt Instrument [Line Items]
Range of weighted average interest rates, by series	0.39%	1.94%
Legacy Sequoia | Maximum
Debt Instrument [Line Items]
Range of weighted average interest rates, by series	2.60%	3.26%
Legacy Sequoia | Certificates with principal balance
Debt Instrument [Line Items]
Certificates	$ 378,087	$ 420,056
Legacy Sequoia | Interest-only certificates
Debt Instrument [Line Items]
Certificates	1,410	1,282
Sequoia Choice
Debt Instrument [Line Items]
Long-term debt	$ 1,861,777	$ 2,037,198
Number of series | series	10	9
Sequoia Choice | Revision of Prior Period, Accounting Standards Update, Adjustment
Debt Instrument [Line Items]
Long-term debt	$ 58,871	$ 40,965
Sequoia Choice | Minimum
Debt Instrument [Line Items]
Range of weighted average interest rates, by series	2.22%	4.40%
Sequoia Choice | Maximum
Debt Instrument [Line Items]
Range of weighted average interest rates, by series	5.04%	5.05%
Sequoia Choice | Certificates with principal balance
Debt Instrument [Line Items]
Certificates	$ 1,793,901	$ 1,979,719
Sequoia Choice | Interest-only certificates
Debt Instrument [Line Items]
Certificates	9,005	16,514
Freddie Mac SLST
Debt Instrument [Line Items]
Long-term debt	$ 1,812,008	$ 1,918,322
Range of weighted average interest rates, by series	3.50%	3.50%
Number of series | series	2	2
Freddie Mac SLST | Revision of Prior Period, Accounting Standards Update, Adjustment
Debt Instrument [Line Items]
Long-term debt	$ 22,069	$ 45,349
Freddie Mac SLST | Certificates with principal balance
Debt Instrument [Line Items]
Certificates	1,765,505	1,842,682
Freddie Mac SLST | Interest-only certificates
Debt Instrument [Line Items]
Certificates	24,434	30,291
Freddie Mac K-Series
Debt Instrument [Line Items]
Long-term debt	$ 464,691	$ 4,156,239
Range of weighted average interest rates, by series	3.39%
Number of series | series	1	5
Freddie Mac K-Series | Revision of Prior Period, Accounting Standards Update, Adjustment
Debt Instrument [Line Items]
Long-term debt	$ 32,605	$ 93,559
Freddie Mac K-Series | Minimum
Debt Instrument [Line Items]
Range of weighted average interest rates, by series		3.35%
Freddie Mac K-Series | Maximum
Debt Instrument [Line Items]
Range of weighted average interest rates, by series		4.35%
Freddie Mac K-Series | Certificates with principal balance
Debt Instrument [Line Items]
Certificates	418,212	$ 3,844,789
Freddie Mac K-Series | Interest-only certificates
Debt Instrument [Line Items]
Certificates	13,874	217,891
CAFL
Debt Instrument [Line Items]
Long-term debt	$ 2,417,253	$ 2,001,251
Number of series | series	12	10
CAFL | Revision of Prior Period, Accounting Standards Update, Adjustment
Debt Instrument [Line Items]
Long-term debt	$ (1,546)	$ 36,110
CAFL | Minimum
Debt Instrument [Line Items]
Range of weighted average interest rates, by series	3.19%	3.25%
CAFL | Maximum
Debt Instrument [Line Items]
Range of weighted average interest rates, by series	5.18%	5.36%
CAFL | Certificates with principal balance
Debt Instrument [Line Items]
Certificates	$ 2,323,475	$ 1,875,007
CAFL | Interest-only certificates
Debt Instrument [Line Items]
Certificates	$ 95,324	$ 90,134