MSR (Activity Related to the MSR Portfolio) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Servicing Assets at Fair Value
Securities gains, net - non-qualifying hedges on MSRs		$ 2	$ 0	$ 0
Changes in fair value and settlement of free-standing derivatives purchased to economically hedge the MSR portfolio (Mortgage banking net revenue)	[1]	2	24	90
Recovery of (provision for) MSR impairment (Mortgage banking net revenue)	[1]	0	7	4
MSR Fair Value Adjustment	[1]	$ (122)	$ 0	$ 0

[1] Included in mortgage banking net revenue in the Consolidated Statements of Income.