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Asset-Backed Securities Issued - Additional Information (Details) - Asset-backed securities issued - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Contractual maturities of over five years |  |
Debt Instrument [Line Items] |  |
Contractual maturities of ABS (in years) | 5 years |
Legacy Sequoia |  |
Debt Instrument [Line Items] |  |
Amortization of deferred ABS issuance costs | $ 1 | $ 1
Sequoia Choice |  |
Debt Instrument [Line Items] |  |
Amortization of deferred ABS issuance costs | $ 2 |

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