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, 2014		77
Balance at Dec. 31, 2014	$ 20,573	$ 0	$ 6,423	$ 14,513	$ (494)	$ 131
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASC 853	67	0	0	56	0	11
Net Income	1,035	0	0	1,027	0	8
Other comprehensive income (loss)	109	0	0	0	109	0
Distributions	(10)	0	0	0	0	(10)
Common stock purchases	(36)	$ 0	(3)	(33)	0	0
Balance (shares) at Jun. 30, 2015		77
Balance at Jun. 30, 2015	$ 21,738	$ 0	6,420	15,563	(385)	140
Balance (shares) at Dec. 31, 2015	77	77
Balance at Dec. 31, 2015	$ 22,535	$ 0	6,403	16,906	(908)	134
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	1,034	0	0	1,026	0	8
Other comprehensive income (loss)	(71)	0	0	0	(71)	0
Distributions	(9)	0	0	0	0	(9)
Other equity transactions	$ (10)	$ 0	(1)	0	0	(9)
Balance (shares) at Jun. 30, 2016	77	77
Balance at Jun. 30, 2016	$ 23,499	$ 0	$ 6,404	$ 17,932	$ (979)	$ 142