MSR (Activity Related to Mortgage Banking Net Revenue) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale
Residential mortgage loan sales	[1]	$ 1,446	$ 1,593	$ 3,919	$ 4,740
Origination fees and gains on loan sales		25	40	77	106
Gross mortgage servicing fees		$ 56	$ 56	$ 162	$ 152

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