Loans and Allowance for Credit Losses (Details 8) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Carrying amount of the covered assets
Purchased impaired loans	$ 5,141	$ 5,854
Purchased non-impaired loans	5,995	6,407
Other assets	2,204	2,800
Total	13,340	15,061
Commercial loans [Member]
Carrying amount of the covered assets
Purchased impaired loans		68
Purchased non-impaired loans	137	137
Total	137	205
Commercial real estate loans [Member]
Carrying amount of the covered assets
Purchased impaired loans	1,566	1,956
Purchased non-impaired loans	3,790	4,037
Total	5,356	5,993
Residential mortgage loans [Member]
Carrying amount of the covered assets
Purchased impaired loans	3,575	3,830
Purchased non-impaired loans	1,242	1,360
Total	4,817	5,190
Credit card portfolio segment [Member]
Carrying amount of the covered assets
Purchased non-impaired loans	5	6
Total	5	6
Other retail portfolio segment [Member]
Carrying amount of the covered assets
Purchased non-impaired loans	821	867
Total	821	867
Losses reimbursable by FDIC [Member]
Carrying amount of the covered assets
Other assets	2,001	2,526
Total	2,001	2,526
Covered portfolio segment [Member]
Carrying amount of the covered assets
Purchased impaired loans	5,141	5,854
Purchased non-impaired loans	5,995	6,407
Other assets	2,001	2,526
Total	13,137	14,787
Foreclosed real estate [Member]
Carrying amount of the covered assets
Other assets	203	274
Total	$ 203	$ 274