Consolidated Statements of Changes in Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income, Net [Member]	Noncontrolling Interest [Member]
Balance (shares) at Dec. 31, 2015		77
Balance at Dec. 31, 2015	$ 22,535	$ 0	$ 6,403	$ 16,906	$ (908)	$ 134
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	494	0	0	490	0	4
Other comprehensive income (loss)	99	0	0	0	99	0
Distributions	(4)	$ 0	0	0	0	(4)
Balance (shares) at Mar. 31, 2016		77
Balance at Mar. 31, 2016	$ 23,124	$ 0	6,403	17,396	(809)	134
Balance (shares) at Dec. 31, 2016	77	77
Balance at Dec. 31, 2016	$ 24,463	$ 0	6,390	19,448	(1,511)	136
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	560	0	0	556	0	4
Other comprehensive income (loss)	126	0	0	0	126	0
Distributions	(7)	0	0	0	0	(7)
Common stock purchases	(19)		(1)	(18)
Other equity transactions	$ (11)	$ 0	(8)	0	0	(3)
Balance (shares) at Mar. 31, 2017	77	77
Balance at Mar. 31, 2017	$ 25,112	$ 0	$ 6,381	$ 19,986	$ (1,385)	$ 130