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	332			332
Other comprehensive income, net of tax	64				64
Preferred Stock Redemption	(126)	(118)	$ 2	(10)
Stock Issued During Period, Value, Conversion of Convertible Securities	(45)		$ (45)
Company Common Stock Repurchased	$ (45)
Company Common Stock Repurchased, Shares	1,500,000		(1,469,000)
Net activity under employee plans and related tax benefits	$ 24		$ 24
Net activity under employee plans and related tax benefits, shares			902,000
Dividends on preferred stock	(36)			(36)
Dividends on common stock	(41)			(41)
Change in deferred compensation	0			0
Balance (in shares) at Sep. 30, 2016			203,850,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity	7,679	710	$ 4,748	2,212	9
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	$ 469			469
Other comprehensive income, net of tax	65				65
Preferred Stock Redemption	(144)	(144)	$ 2	(2)
Company Common Stock Repurchased	$ (205)		$ (205)
Company Common Stock Repurchased, Shares	5,000,000		(4,689,000)
Net activity under employee plans and related tax benefits	$ 30		$ 30
Net activity under employee plans and related tax benefits, shares			1,316,000
Dividends on preferred stock	(30)			(30)
Dividends on common stock	$ (58)			(58)
Balance (in shares) at Sep. 30, 2017	199,712,000		199,712,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity	$ 7,761	$ 566	$ 4,552	$ 2,700	$ (57)