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		$ 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	517	0	0		513	0	4
Other comprehensive income (loss)	68	0	0		0	68	0
Common stock purchases	(90)	0	(5)		(85)	0	0
Distributions	(9)	$ 0	0		0	0	(9)
Balance (shares) at Mar. 31, 2018		77
Balance at Mar. 31, 2018	28,794	$ 0	6,363		23,719	(1,415)	127
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Long-term income tax receivable	$ (457)			$ (457)
Balance (shares) at Dec. 31, 2018	77	77
Balance at Dec. 31, 2018	$ 29,723	$ 0	6,371		25,624	(1,945)	130
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	625	0	0		622	0	3
Other comprehensive income (loss)	115	0	0		0	115	0
Common stock purchases	(293)	0	(16)		(277)	0	0
Distributions	(7)	$ 0	0		0	0	(7)
Other equity transactions	$ (1)				(1)
Balance (shares) at Mar. 31, 2019	77	77
Balance at Mar. 31, 2019	$ 30,162	$ 0	$ 6,355		$ 25,968	$ (1,830)	$ 126
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Long-term income tax receivable	$ (457)			$ (457)