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	2,076	0	0	2,062	0	14
Other comprehensive income (loss)	(110)	0	0	0	(110)	0
Distributions	(14)	0	0	0	0	(14)
Other equity transactions	9	$ 0	1	0	0	8
Balance (shares) at Sep. 30, 2016		77
Balance at Sep. 30, 2016	$ 24,496	$ 0	6,404	18,968	(1,018)	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	2,212	0	0	2,198	0	14
Other comprehensive income (loss)	1,088	0	0	0	1,088	0
Distributions	(16)	0	0	0	0	(16)
Common stock purchases	(19)	0	(1)	(18)	0	0
Conversion of Stock, Amount Converted	(100)	0	(6)	(94)	0	0
Other equity transactions	$ (24)	$ 0	(21)	0	0	(3)
Balance (shares) at Sep. 30, 2017	77	77
Balance at Sep. 30, 2017	$ 27,604	$ 0	$ 6,362	$ 21,534	$ (423)	$ 131