Receivables Held for Investment, net - Additional Information (Detail) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
		Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Initial lower of amortized cost or fair value adjustment		$ 541	$ 587	$ 234
Receivables, collateralizing long-term debt			750	1,654
Secured financing			404	879
Deferred origination fees				71
Net unamortized premium on our receivables				35
Other Revenue [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Initial lower of amortized cost or fair value adjustment	[1]		$ 11	$ 0	$ 113

[1] Represents the portion of the initial lower of amortized cost or fair value adjustment attributable to non-credit factors which are recorded as a component of total other revenues in the consolidated statement income (loss) as it reflects the impact on value caused by current marketplace conditions including changes in interest rates.