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	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	9
Balance (shares) at Jun. 30, 2016		77
Balance at Jun. 30, 2016	$ 23,499	$ 0	6,404	17,932	(979)	142
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	1,139	0	0	1,130	0	9
Other comprehensive income (loss)	422	0	0	0	422	0
Distributions	(12)	0	0	0	0	(12)
Common stock purchases	(19)	0	(1)	(18)	0	0
Conversion of Stock, Amount Converted	(100)	0	(6)	(94)	0	0
Other equity transactions	$ (23)	$ 0	(21)	1	0	(3)
Balance (shares) at Jun. 30, 2017	77	77
Balance at Jun. 30, 2017	$ 25,870	$ 0	$ 6,362	$ 20,467	$ (1,089)	$ 130