Consolidated Statements of Changes in Equity Statement (USD $) In Millions, unless otherwise specified	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss, Net[Member]	Noncontrolling Interest [Member]
Balance at Dec. 31, 2010	$ 7,311	$ 41	$ 0	$ 4,479	$ 2,798	$ (7)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	127				127
Other comprehensive loss	(1)					(1)
Preferred stock dividends declared	(1)				(1)
Common stock dividends declared	(550)				(550)
Balance at Mar. 31, 2011	6,886	41	0	4,479	2,374	(8)	0
Balance at Dec. 31, 2011	7,312	41	0	4,479	2,801	(9)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	151				151
Preferred stock dividends declared	(1)				(1)
Common stock dividends declared	(50)				(50)
Balance at Mar. 31, 2012	$ 7,412	$ 41	$ 0	$ 4,479	$ 2,901	$ (9)	$ 0