Fair Value of Assets and Liabilities - Additional Information about Servicing Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Servicing Assets
Servicing Assets, Fair value, Beginning Balance	$ 64,006
Servicing Assets, Fair value, Ending Balance	89,680	$ 64,006
Fair Value, Measurements, Recurring
Servicing Assets
Servicing Assets, Fair value, Beginning Balance	64,006	33,676
Issuances	79,692	55,403
Change in fair value, included in investor fees	(58,172)	(31,233)
Other net changes included in deferred revenue	4,154	6,160
Servicing Assets, Fair value, Ending Balance	89,680	64,006
Asset-backed subordinated securities related to Company-sponsored Structured Program transactions
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Fair value at beginning of period	60,279	10,029
Additions	118,721	65,098
Redemptions	(17,900)	(2,742)
Cash received	(45,701)	(9,329)
Change in unrealized gain (loss)	(992)	201
Other-than-temporary impairment	(3,611)	(2,978)
Fair value at end of period	$ 110,796	$ 60,279

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Charge-offs

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- Definition

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Retirements

+ References

No definition available.

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- Definition

Amount of gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-Section 50
-Paragraph 2
-Subparagraph (c)(1)
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- Definition

Amount of purchases of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The value of new servicing assets, subsequently measured at fair value, acquired or created during the current period through purchases or from transfers of financial assets.

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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Amount of increase (decrease) in fair value from changes in the inputs, assumptions, or model used to calculate the fair value of the contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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Amount of increase (decrease) in fair value from changes classified as other for a contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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