Consolidated Statements Of Changes In Shareholders' Equity - USD ($) shares in Thousands, $ 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	$ 7,634	$ 710	$ 4,725	$ 2,321	$ (122)
Balance (in shares) at Dec. 31, 2016			203,085
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the period	139			139
Other comprehensive income, net of tax	11				11
Stock Issued During Period, Value, Conversion of Convertible Securities	(45)		$ (45)
Company Common Stock Repurchased	$ (45)
Company Common Stock Repurchased, Shares	1,100		(1,060)
Net activity under employee plans and related tax benefits	$ 16		$ 16
Net activity under employee plans and related tax benefits, shares			570
Dividends on preferred stock	(10)			(10)
Dividends on common stock	(15)			(15)
Balance (in shares) at Mar. 31, 2017			202,595
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity	7,730	710	$ 4,696	2,435	(111)
Stockholders' Equity	$ 7,679	566	$ 4,445	2,807	(139)
Balance (in shares) at Dec. 31, 2017	197,532		197,532
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the period	$ 238			238
Other comprehensive income, net of tax	(128)				(128)
Preferred Stock Redemption	1			1
Company Common Stock Repurchased	$ (115)		$ (115)
Net Shares Issued From Stock Warrant Exercises	1,000		1,042
Company Common Stock Repurchased, Shares	2,000		(2,151)
Net activity under employee plans and related tax benefits	$ 16		$ 16
Net activity under employee plans and related tax benefits, shares			627
Dividends on preferred stock	(7)			(7)
Dividends on common stock	$ (40)			(40)
Balance (in shares) at Mar. 31, 2018	197,050		197,050
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity	$ 7,644	$ 566	$ 4,346	$ 2,999	$ (267)