Securities (Realized Gains and Losses Recognized in Income from Available-for-Sale Securities) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments, Unrealized Loss Position
OTTI	[1]	$ (16)	$ (5)	$ (24)
Available-for-sale Securities
Investments, Unrealized Loss Position
Realized gains		72	97	70
Realized losses		(45)	(76)	(9)
OTTI		(16)	(5)	(24)
Net realized gains (losses)	[2]	$ 11	$ 16	$ 37

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

[2] (a) Excludes net losses on interest-only mortgage-backed securities of $ 4 , $ 4 and $ 17 for the years ended December 31, 2016 , 2015 and 2014 , respectively