Consolidated Statements of Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Treasury Stock
Balance at beginning of period at Dec. 31, 2013		$ 4	$ 844	$ (60)	$ 6,598	$ (3,801)
Balance at beginning of period (in shares) at Dec. 31, 2013		396				139
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 754				754
Other comprehensive loss	(3)			(3)
Share-based compensation			49
Shares issued under stock plans including income tax benefits			4			$ 64
Shares issued under stock plans including income tax benefits (in shares)						(2)
Purchases of treasury stock						$ (1,158)
Purchases of treasury stock (in shares)						18
Balance at end of period at Dec. 31, 2014		$ 4	897	(63)	7,352	$ (4,895)
Balance at end of period (in shares) at Dec. 31, 2014		396				155
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	712				712
Other comprehensive loss	(11)			(11)
Share-based compensation			65
Shares issued under stock plans including income tax benefits			(10)			$ 80
Shares issued under stock plans including income tax benefits (in shares)						(2)
Purchases of treasury stock						$ (1,471)
Purchases of treasury stock (in shares)						17
Balance at end of period at Dec. 31, 2015	2,660	$ 4	952	(74)	8,064	$ (6,286)
Balance at end of period (in shares) at Dec. 31, 2015		396				170
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	930				930
Other comprehensive loss	(2)			(2)
Share-based compensation			68
Shares issued under stock plans including income tax benefits			0			$ 83
Shares issued under stock plans including income tax benefits (in shares)						(2)
Purchases of treasury stock						$ (1,198)
Purchases of treasury stock (in shares)						12
Balance at end of period at Dec. 31, 2016	$ 2,541	$ 4	$ 1,020	$ (76)	$ 8,994	$ (7,401)
Balance at end of period (in shares) at Dec. 31, 2016		396				180