MSR (Activity Related to Mortgage Banking Net Revenue) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale
Residential mortgage loan sales	[1]	$ 1,593	$ 1,846	$ 4,740	$ 4,591
Origination fees and gains on loan sales		40	61	106	156
Gross Mortgage Servicing Fees		$ 56	$ 49	$ 152	$ 151

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