CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Millions, $ in Millions	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]	Total
Beginning Balance at Dec. 31, 2014	$ 1	$ 5,798	$ (6,111)	$ 6,181	$ (584)	$ 75	$ 5,360
Beginning Balance (in shares) at Dec. 31, 2014	82.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income				(240)		15	(225)
Other comprehensive income (loss)					10		10
Distributions to noncontrolling interests						(16)	(16)
Cash dividends declared				(213)			(213)
Shares issued:
Employee savings plans		120					120
Employee savings plans (in shares)	1.1
Exercise of stock options		74					74
Exercise of stock options (in shares)	0.7
Employee stock purchase plan		34					34
Employee stock purchase plan (in shares)	0.3
Vesting of restricted stock and performance units (in shares)	0.7
Repurchases of common stock to satisfy tax withholding obligations		(33)					(33)
Repurchases of common stock to satisfy tax withholding obligations (in shares)	(0.3)
Stock-based compensation expense		49					49
Treasury stock purchased			(740)				(740)
Treasury stock purchased (in shares)	(6.4)
Retirement of Convertible Contingent Debt Securities		(161)					(161)
Other		9					9
Ending Balance at Dec. 31, 2015	$ 1	6,051	(6,851)	5,728	(574)	74	4,429
Ending Balance (in shares) at Dec. 31, 2015	78.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income				710		14	724
Other comprehensive income (loss)					(152)		(152)
Distributions to noncontrolling interests						(17)	(17)
Cash dividends declared				(220)			(220)
Shares issued:
Employee savings plans		115					115
Employee savings plans (in shares)	0.9
Exercise of stock options		53					53
Exercise of stock options (in shares)	0.6
Employee stock purchase plan		31					31
Employee stock purchase plan (in shares)	0.4
Vesting of restricted stock and performance units (in shares)	0.5
Repurchases of common stock to satisfy tax withholding obligations		(21)					(21)
Repurchases of common stock to satisfy tax withholding obligations (in shares)	(0.3)
Stock-based compensation expense		49					49
Treasury stock purchased			(373)				(373)
Treasury stock purchased (in shares)	(3.0)
Other		6					6
Ending Balance at Dec. 31, 2016	$ 1	6,284	(7,224)	6,218	(726)	71	4,624
Ending Balance (in shares) at Dec. 31, 2016	77.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income				677		16	693
Other comprehensive income (loss)					35		35
Distributions to noncontrolling interests						(19)	(19)
Cash dividends declared				(236)			(236)
Shares issued:
Employee savings plans		113					113
Employee savings plans (in shares)	0.8
Exercise of stock options		46					46
Exercise of stock options (in shares)	0.5
Employee stock purchase plan		32					32
Employee stock purchase plan (in shares)	0.2
Vesting of restricted stock and performance units (in shares)	0.3
Repurchases of common stock to satisfy tax withholding obligations		(18)					(18)
Repurchases of common stock to satisfy tax withholding obligations (in shares)	(0.1)
Stock-based compensation expense		53					53
Treasury stock purchased			(180)				(180)
Treasury stock purchased (in shares)	(1.0)
Other		8					8
Ending Balance at Dec. 31, 2017	$ 1	$ 6,518	$ (7,404)	$ 6,659	$ (691)	$ 68	$ 5,151
Ending Balance (in shares) at Dec. 31, 2017	77.9