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]
Balance at Dec. 31, 2010	$ 7,311	$ 41	$ 0	$ 4,479	$ 2,798	$ (7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	425				425
Preferred stock dividends declared	(2)				(2)
Common stock dividends declared	(550)				(550)
Balance at Sep. 30, 2011	7,184	41	0	4,479	2,671	(7)
Balance at Dec. 31, 2011	7,312	41	0	4,479	2,801	(9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	493				493
Preferred stock dividends declared	(2)				(2)
Common stock dividends declared	(150)				(150)
Balance at Sep. 30, 2012	$ 7,653	$ 41	$ 0	$ 4,479	$ 3,142	$ (9)