Consolidated Statements of Changes in Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Long-term income tax receivable [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income, Net [Member]	Noncontrolling Interest [Member]
Balance (shares) at Dec. 31, 2017		77
Balance at Dec. 31, 2017	$ 28,308	$ 0	$ 6,368	$ 0	$ 22,206	$ (398)	$ 132
Increase (Decrease) in Stockholders' Equity [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification					1,085	(1,085)
Net Income	2,302	0	0		2,286	0	16
Other comprehensive income (loss)	(184)	0	0		0	(184)	0
Reclassification of long-term income tax receivable	(609)			(609)
Long-term income tax receivable adjustments	0			115	(115)
Common stock purchases	(107)	0	(6)		(101)	0	0
Distributions	(17)	0	0		0	0	(17)
Other equity transactions	(5)	$ 0	(5)		0	0	0
Balance (shares) at Sep. 30, 2018		77
Balance at Sep. 30, 2018	29,688	$ 0	6,357	(494)	25,361	(1,667)	131
Balance (shares) at Jun. 30, 2018		77
Balance at Jun. 30, 2018	28,304	$ 0	6,358	(494)	23,976	(1,665)	129
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	1,409	0	0		1,401	0	8
Other comprehensive income (loss)	(2)	0	0		0	(2)	0
Common stock purchases	(17)	0	(1)		(16)	0	0
Distributions	(5)	0	0		0	0	(5)
Other equity transactions	(1)	$ 0	0		0	0	(1)
Balance (shares) at Sep. 30, 2018		77
Balance at Sep. 30, 2018	$ 29,688	$ 0	6,357	(494)	25,361	(1,667)	131
Balance (shares) at Dec. 31, 2018	77	77
Balance at Dec. 31, 2018	$ 29,723	$ 0	6,371	(457)	25,624	(1,945)	130
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	2,457	0	0		2,443	0	14
Other comprehensive income (loss)	(134)	0	0		0	(134)	0
Common stock purchases	(293)	0	(16)		(277)	0	0
Distributions	(16)	0	0		0	0	(16)
Other equity transactions	$ 3	$ 0	0		(1)	0	4
Balance (shares) at Sep. 30, 2019	77	77
Balance at Sep. 30, 2019	$ 31,740	$ 0	6,355	(457)	27,789	(2,079)	132
Balance (shares) at Jun. 30, 2019		77
Balance at Jun. 30, 2019	30,787	$ 0	6,355	(457)	26,651	(1,888)	126
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	1,144	0	0		1,137	0	7
Other comprehensive income (loss)	(191)	0	0		0	(191)	0
Distributions	(6)	0	0		0	0	(6)
Other equity transactions	$ 6	$ 0	0		1	0	5
Balance (shares) at Sep. 30, 2019	77	77
Balance at Sep. 30, 2019	$ 31,740	$ 0	$ 6,355	$ (457)	$ 27,789	$ (2,079)	$ 132