Consolidated Statements Of Changes In Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Capital Surplus	Accumulated Other Comprehensive Loss	Retained Earnings	Treasury Stock
BALANCE at Dec. 31, 2013	$ 7,150	$ 1,141	$ 2,179	$ (391)	$ 6,318	$ (2,097)
BALANCE (in shares) at Dec. 31, 2013		182.3
Net income	593				593
Other comprehensive income (loss), net of tax	(21)			(21)
Cash dividends declared on common stock	(143)				(143)
Purchase of common stock	(260)					(260)
Purchase of common stock (in shares)		(5.4)
Net issuance of common stock under employee stock plans	45		(27)		(24)	96
Net issuance of common stock under employee stock plans (in shares)		2.1
Share-based compensation	38		38
Other	0		(2)			2
BALANCE at Dec. 31, 2014	7,402	$ 1,141	2,188	(412)	6,744	(2,259)
BALANCE (in shares) at Dec. 31, 2014		179.0
Net income	521				521
Other comprehensive income (loss), net of tax	(17)			(17)
Cash dividends declared on common stock	(148)				(148)
Purchase of common stock	(240)					(240)
Purchase of common stock (in shares)		(5.3)
Adjustment To Paid In Capital, Warrant Repurchased And Retired	(10)		(10)
Net issuance of common stock under employee stock plans	14		(22)		(11)	47
Net issuance of common stock under employee stock plans (in shares)		1.0
Net issuance of common stock for warrants	0		(21)		(22)	43
Net issuance of common stock for warrants (in shares)		1.0
Share-based compensation	38		38
BALANCE at Dec. 31, 2015	7,560	$ 1,141	2,173	(429)	7,084	(2,409)
BALANCE (in shares) at Dec. 31, 2015		175.7
Net income	477				477
Other comprehensive income (loss), net of tax	46			46
Cash dividends declared on common stock	(154)				(154)
Purchase of common stock	(310)					(310)
Purchase of common stock (in shares)		(6.8)
Net issuance of common stock under employee stock plans	143		(15)		(27)	185
Net issuance of common stock under employee stock plans (in shares)		4.1
Net issuance of common stock for warrants	0		(57)		(49)	106
Net issuance of common stock for warrants (in shares)		2.3
Share-based compensation	34		34
BALANCE at Dec. 31, 2016	$ 7,796	$ 1,141	$ 2,135	$ (383)	$ 7,331	$ (2,428)
BALANCE (in shares) at Dec. 31, 2016		175.3