Sales of Receivables and Servicing Rights - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014	Dec. 31, 2014
Mortgage Loans On Real Estate [Line Items]
Residential mortgage loan sales	[1]	$ 1,421		$ 1,228	$ 3,798	[2]	$ 4,423
Sevicing of residential mortgage loans for other investors		$ 60,300			$ 60,300			$ 65,400
Residential Mortgage Loans | Troubled Debt Restructuring
Mortgage Loans On Real Estate [Line Items]
Gain on sale of HFS loans			$ 37

[1] Represents the unpaid principal balance at the time of the sale.

[2] Excludes $568 of HFS residential mortgage loans previously modified in a TDR that were sold during the first quarter of 2015.