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	472	0	0	469	0	3
Other comprehensive income (loss)	(235)	0	0	0	(235)	0
Distributions	(6)	0	0	0	0	(6)
Common stock purchases	(36)	$ 0	(3)	(33)	0	0
Balance (shares) at Mar. 31, 2015		77
Balance at Mar. 31, 2015	$ 20,835	$ 0	6,420	15,005	(729)	139
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	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	77
Balance at Mar. 31, 2016	$ 23,124	$ 0	$ 6,403	$ 17,396	$ (809)	$ 134