MSR (Activity Related to the MSR Portfolio) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Servicing Assets at Fair Value
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights		$ (4)	$ 2	$ (17)	$ 2
MSR fair value adjustments due to change in inputs or assumptions	[1]	21	(17)	78	(13)
Interest Rate Contract | Servicing Rights | Mortgage Banking Revenue
Servicing Assets at Fair Value
Changes in fair value and settlement of free-standing derivatives purchased to economically hedge the MSR portfolio (Mortgage banking net revenue)	[1]	$ (16)	$ 16	$ (65)	$ 15

[1] (a) Included in mortgage banking net revenue in the Condensed Consolidated Statements of Income.