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	893	0	0		885	0	8
Other comprehensive income (loss)	(182)	0	0		0	(182)	0
Reclassification of long-term income tax receivable	(609)			(609)
Long-term income tax receivable adjustments	0			115	(115)
Common stock purchases	(90)	0	(5)		(85)	0	0
Distributions	(12)	0	0		0	0	(12)
Other equity transactions	(4)	$ 0	(5)		0	0	1
Balance (shares) at Jun. 30, 2018		77
Balance at Jun. 30, 2018	28,304	$ 0	6,358	(494)	23,976	(1,665)	129
Balance (shares) at Mar. 31, 2018		77
Balance at Mar. 31, 2018	28,794	$ 0	6,363	0	23,719	(1,415)	127
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	376	0	0		372	0	4
Other comprehensive income (loss)	(250)	0	0		0	(250)	0
Reclassification of long-term income tax receivable	(609)			(609)
Long-term income tax receivable adjustments	0			115	(115)
Distributions	(3)	0	0		0	0	(3)
Other equity transactions	(4)	$ 0	(5)		0	0	1
Balance (shares) at Jun. 30, 2018		77
Balance at Jun. 30, 2018	$ 28,304	$ 0	6,358	(494)	23,976	(1,665)	129
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	1,313	0	0		1,306	0	7
Other comprehensive income (loss)	57	0	0		0	57	0
Common stock purchases	(293)	0	(16)		(277)	0	0
Distributions	(10)	0	0		0	0	(10)
Other equity transactions	$ (3)	$ 0	0		(2)	0	(1)
Balance (shares) at Jun. 30, 2019	77	77
Balance at Jun. 30, 2019	$ 30,787	$ 0	6,355	(457)	26,651	(1,888)	126
Balance (shares) at Mar. 31, 2019		77
Balance at Mar. 31, 2019	30,162	$ 0	6,355	(457)	25,968	(1,830)	126
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	688	0	0		684	0	4
Other comprehensive income (loss)	(58)	0	0		0	(58)	0
Distributions	(3)	0	0		0	0	(3)
Other equity transactions	$ (2)	$ 0	0		(1)	0	(1)
Balance (shares) at Jun. 30, 2019	77	77
Balance at Jun. 30, 2019	$ 30,787	$ 0	$ 6,355	$ (457)	$ 26,651	$ (1,888)	$ 126