CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock, at Cost	Non-controlling Interests
Balance, value at Dec. 31, 2016	$ 4,660	$ 2	$ 2,545	$ 6,613	$ (72)	$ (4,460)	$ 32
Balance, shares at Dec. 31, 2016		137.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	379			357			22
Other comprehensive loss, net of taxes	12				12
Dividends declared	(123)			(123)
Distributions to noncontrolling interests	(20)						(20)
Issuance of common stock under benefit plans	12		6			6
Stock-based compensation expense	37		35			2
Exercise of stock options, value	97		2			95
Exercise of stock options, shares		2.0
Shares to cover employee payroll tax withholdings on stock issued under stock-based compensation plans, value	(23)		(23)
Purchases of treasury stock, value	(300)					$ (300)
Purchases of treasury stock, shares		(3.0)				(3.0)
Other	2						2
Balance, value at Jun. 30, 2017	4,733	$ 2	2,565	6,847	(60)	$ (4,657)	36
Balance, shares at Jun. 30, 2017		136.0
Balance, Value at Dec. 31, 2016	77
Redeemable Non-controlling Interest [Abstract]
Net income	3
Balance, Value at Jun. 30, 2017	80
Balance, value at Dec. 31, 2017	4,955	$ 2	2,612	7,138	(48)	(4,783)	34
Balance, shares at Dec. 31, 2017		135.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	419			396			23
Other comprehensive loss, net of taxes	(7)				(7)
Dividends declared	(135)			(135)
Distributions to noncontrolling interests	(21)						(21)
Issuance of common stock under benefit plans	13		6			7
Stock-based compensation expense	34		32			2
Exercise of stock options, value	71		3			68
Exercise of stock options, shares		1.0
Shares to cover employee payroll tax withholdings on stock issued under stock-based compensation plans, value	(20)		(20)
Purchases of treasury stock, value	(50)					$ (50)
Purchases of treasury stock, shares						(0.5)
Sale of noncontrolling interest in subsidiaries	4						4
Reclassification of stranded tax effects resulting from enactment of the Tax Cuts and Jobs Act				2	(2)
Balance, value at Jun. 30, 2018	5,263	$ 2	$ 2,633	$ 7,401	$ (57)	$ (4,756)	$ 40
Balance, shares at Jun. 30, 2018		136.0
Balance, Value at Dec. 31, 2017	80
Redeemable Non-controlling Interest [Abstract]
Net income	3
Distributions to noncontrolling interests	(7)
Balance, Value at Jun. 30, 2018	$ 76