MSR (Activity Related to the MSR Portfolio) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Servicing Assets at Fair Value
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights		$ (13)	$ 0
MSR Fair Value Adjustment	[1]	(28)	23
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]	$ (49)	$ (1)

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