Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity	$ 7,507	$ 828	$ 4,767	$ 1,967	$ (55)
Balance (in shares) at Dec. 31, 2015			204,417,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the period	204			204
Other comprehensive income, net of tax	78				78
Preferred Stock Redemption In Period	(126)	(118)	$ 2	(10)
Net activity under employee plans and related tax benefits	14		$ 14
Net activity under employee plans and related tax benefits, shares			687,000
Dividends on preferred stock	(25)			(25)
Dividends on common stock	(24)			(24)
Change in deferred compensation	(2)			(2)
Balance (in shares) at Jun. 30, 2016			205,104,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity	7,626	710	$ 4,783	2,110	23
Stockholders' Equity	$ 7,634	710	$ 4,725	2,321	(122)
Balance (in shares) at Dec. 31, 2016	203,085,000		203,085,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the period	$ 308			308
Other comprehensive income, net of tax	73				73
Preferred Stock Redemption In Period	(144)	(144)	$ 2	(2)
Stock Repurchased and Retired During Period, Value	$ (90)		$ (90)
Stock Repurchased During Period, Shares	2,000,000		(2,158,000)
Net activity under employee plans and related tax benefits	$ 23		$ 23
Net activity under employee plans and related tax benefits, shares			1,204,000
Dividends on preferred stock	(23)			(23)
Dividends on common stock	$ (32)			(32)
Balance (in shares) at Jun. 30, 2017	202,131,000		202,131,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity	$ 7,749	$ 566	$ 4,660	$ 2,572	$ (49)