Condensed Consolidated Statements of Stockholders' Deficit - USD ($) $ in Millions	Total	Common Stock [Member]	Capital in Excess of Par Value [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Deficit [Member]	Equity Attributable to Noncontrolling Interests [Member]
Balances at Dec. 31, 2016	$ (5,633)	$ 4		$ (338)	$ (6,968)	$ 1,669
Balance, shares at Dec. 31, 2016		370,536,000
Comprehensive income	795			18	659	118
Repurchase of common stock	(424)		$ (32)		(392)
Repurchase of common stock, shares		(5,121,000)
Share-based benefit plans	35		35
Share-based benefit plans, shares		3,280,000
Distributions	(145)					(145)
Other	15		(3)			18
Balance at Mar. 31, 2017	(5,357)	$ 4		(320)	(6,701)	1,660
Balance, shares at Mar. 31, 2017		368,695,000
Balances at Dec. 31, 2016	(5,633)	$ 4		(338)	(6,968)	1,669
Balance, shares at Dec. 31, 2016		370,536,000
Comprehensive income	2,172
Balance at Sep. 30, 2017	(5,066)	$ 4		(268)	(6,516)	1,714
Balance, shares at Sep. 30, 2017		356,980,000
Balances at Mar. 31, 2017	(5,357)	$ 4		(320)	(6,701)	1,660
Balance, shares at Mar. 31, 2017		368,695,000
Comprehensive income	822			27	657	138
Repurchase of common stock	(542)		(83)		(459)
Repurchase of common stock, shares		(6,404,000)
Share-based benefit plans	82		82
Share-based benefit plans, shares		604,000
Distributions	(103)					(103)
Other	(19)		(1)			(18)
Balance at Jun. 30, 2017	(5,079)	$ 4		(293)	(6,503)	1,713
Balance, shares at Jun. 30, 2017		362,895,000
Comprehensive income	555			25	426	104
Repurchase of common stock	(509)		(70)		(439)
Repurchase of common stock, shares		(6,322,000)
Share-based benefit plans	71		71
Share-based benefit plans, shares		407,000
Distributions	(115)					(115)
Other	(11)		1			(12)
Balance at Sep. 30, 2017	(5,066)	$ 4		(268)	(6,516)	1,714
Balance, shares at Sep. 30, 2017		356,980,000
Comprehensive income	631			(10)	474	167
Repurchase of common stock	(576)		(86)		(490)
Repurchase of common stock, shares		(7,245,000)
Share-based benefit plans	93		93
Share-based benefit plans, shares		357,000
Distributions	(85)					(85)
Other	(8)		7			(15)
Balance at Dec. 31, 2017	(4,995)	$ 4		(278)	(6,532)	1,811
Balance, shares at Dec. 31, 2017		350,092,000
Comprehensive income	1,363			81	1,144	138
Repurchase of common stock	(423)				(423)
Repurchase of common stock, shares		(4,370,000)
Share-based benefit plans	(114)				(114)
Share-based benefit plans, shares		5,265,000
Cash dividends declared ($0.35 per share)	(126)				(126)
Distributions	(92)					(92)
Other	47					47
Balance at Mar. 31, 2018	(4,434)	$ 4		(197)	(6,051)	1,810
Balance, shares at Mar. 31, 2018		350,987,000
Balances at Dec. 31, 2017	(4,995)	$ 4		(278)	(6,532)	1,811
Balance, shares at Dec. 31, 2017		350,092,000
Comprehensive income	$ 3,156
Repurchase of common stock, shares	(11,558,000)
Balance at Sep. 30, 2018	$ (3,730)	$ 3		(266)	(5,342)	1,875
Balance, shares at Sep. 30, 2018		345,086,000
Balances at Mar. 31, 2018	(4,434)	$ 4		(197)	(6,051)	1,810
Balance, shares at Mar. 31, 2018		350,987,000
Comprehensive income	902			(64)	820	146
Repurchase of common stock	(470)	$ (1)	(93)		(376)
Repurchase of common stock, shares		(4,670,000)
Share-based benefit plans	96		96
Share-based benefit plans, shares		443,000
Cash dividends declared ($0.35 per share)	(124)				(124)
Distributions	(93)					(93)
Other	2		3			(1)
Balance at Jun. 30, 2018	(4,125)	$ 3		(261)	(5,731)	1,864
Balance, shares at Jun. 30, 2018		346,760,000
Comprehensive income	891			(5)	759	137
Repurchase of common stock	(302)		(55)		(247)
Repurchase of common stock, shares		(2,518,000)
Share-based benefit plans	54		54
Share-based benefit plans, shares		844,000
Cash dividends declared ($0.35 per share)	(123)				(123)
Distributions	(130)					(130)
Other	(5)		$ (1)			(4)
Balance at Sep. 30, 2018	$ (3,730)	$ 3		$ (266)	$ (5,342)	$ 1,875
Balance, shares at Sep. 30, 2018		345,086,000