Shareholders' Equity (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended		3 Months Ended			12 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended	3 Months Ended
	Apr. 30, 2011	Nov. 30, 2008	Mar. 31, 2012	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2011	Jun. 30, 2011	Sep. 30, 2011 Retained Earnings [Member]	Sep. 30, 2011 Retained Earnings [Member]	Dec. 31, 2010 Retained Earnings [Member]	Mar. 31, 2011 Series B Preferred Stock [Member]	Dec. 31, 2008 Series B Preferred Stock [Member]	Mar. 31, 2012 Common Stock [Member] Maximum [Member]
Shareholders' Equity (Textual) [Abstract]
Treasury Stock, Value											$ 2,500		$ 344
Issuance of preferred stock to the U.S. Treasury												2,500
Warrants repurchased	70
Shareholders' Equity (Additional) (Textual) [Abstract]
Amortization of discount on preferred stock including deemed dividend					49
Common Stock general repurchase program			312
Common Stock employee compensation and benefit program			32
Elimination of dividends				31
Discount amortization				4			140
Amount paid to US treasury during the investment period						2,867
Return to US treasury above initial investment		367
Cumulative effect adjustment to beginning balance of Retained Earnings								$ 45	$ 45	$ 45