Securities (Realized Gains and Losses Recognized in Income from Available-for-Sale Securities) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Investments, Unrealized Loss Position
OTTI	[1]	$ (14)	$ (3)	$ (24)	$ (5)
Available-for-sale Securities
Investments, Unrealized Loss Position
Realized gains		21	15	30	29
Realized losses		(7)	(4)	(8)	(8)
OTTI		(14)	(3)	(24)	(5)
Net realized gains (losses)	[2]	$ 0	$ 8	$ (2)	$ 16

[1] (a) Included in securities gains, net in the Condensed Consolidated Statements of Income.

[2] (a) Excludes n et losses on interest-only mortgage- backed securities of $ 2 and $ 1 for the three and six months ended June 30, 2017 , respectively, and $ 3 and $ 8 for the three and six months ended June 30, 2016 , respectively.