Consolidated Statements of Changes in Equity (USD $) In Millions, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss, Net [Member]	Noncontrolling Interests [Member]
Balance at Dec. 31, 2011	$ 14,265	$ 0	$ 5,423	$ 9,310	$ (641)	$ 173
Balance (shares) at Dec. 31, 2011		75
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	379	0	0	375	0	4
Other comprehensive income (loss)	154	0	0	0	154	0
Distributions	(8)	0	0	0	0	(8)
Balance at Mar. 31, 2012	14,790	0	5,423	9,685	(487)	169
Balance (shares) at Mar. 31, 2012		75
Balance at Dec. 31, 2012	15,910	0	5,423	10,782	(463)	168
Balance (shares) at Dec. 31, 2012	75	75
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	444
Net Income	442	0	0	438	0	4
Other comprehensive income (loss)	(122)	0	0	0	(122)	0
Distributions	(7)	0	0	0	0	(7)
Other equity transactions	3	0	0	0	0	3
Balance at Mar. 31, 2013	$ 16,226	$ 0	$ 5,423	$ 11,220	$ (585)	$ 168
Balance (shares) at Mar. 31, 2013	75	75