Consolidated Statements of Changes in Shareholders' 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, 2011	$ 7,312	$ 41	$ 0	$ 4,479	$ 2,801	$ (9)
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)
Balance at Dec. 31, 2012	7,644	41	0	4,479	3,136	(12)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	160				160
Preferred stock dividends declared	(1)				(1)
Common stock dividends declared	(150)				(150)
Balance at Mar. 31, 2013	$ 7,653	$ 41	$ 0	$ 4,479	$ 3,145	$ (12)