Goodwill and Other Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended		3 Months Ended	12 Months Ended		3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2009	Mar. 31, 2009 Austin Capital Management [Member]	Dec. 31, 2011 Community Banking [Member]	Dec. 31, 2010 Community Banking [Member]	Mar. 31, 2009 Corporate Banking [Member]	Dec. 31, 2011 Corporate Banking [Member]	Dec. 31, 2009 Corporate Banking [Member]
Changes in the carrying amount of goodwill
Beginning Balance	$ 917	$ 917		$ 917	$ 917		$ 0	$ 0
Impairment losses based on results of interim impairment testing						(223)
Ending Balance	917	917		917	917		0	0
Goodwill and Other Intangible Assets (Textual) [Abstract]
Pre tax Impairment charge related to discontinued operation reclassified to income loss from discontinued operation net of tax			$ 27