Loans and Allowance for Loan Losses (Details 6) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Aging of loans held for investment, excluding FDIC covered loans
Current	$ 53,023	$ 51,913
30 to 89 days past due	293	382
90 days or more past due	277	296
Total past due	570	678
Total loans held for investment, excluding FDIC covered loans	53,593	52,591
Commercial and Industrial [Member]
Aging of loans held for investment, excluding FDIC covered loans
Current	20,359	20,033
30 to 89 days past due	66	121
90 days or more past due	34	37
Total past due	100	158
Total loans held for investment, excluding FDIC covered loans	20,459	20,191
Commercial Mortgage [Member]
Aging of loans held for investment, excluding FDIC covered loans
Current	8,151	8,111
30 to 89 days past due	23	49
90 days or more past due	14	15
Total past due	37	64
Total loans held for investment, excluding FDIC covered loans	8,188	8,175
Construction Loans [Member]
Aging of loans held for investment, excluding FDIC covered loans
Current	598	855
30 to 89 days past due	15
90 days or more past due		15
Total past due	15	15
Total loans held for investment, excluding FDIC covered loans	613	870
Commercial [Member]
Aging of loans held for investment, excluding FDIC covered loans
Current	29,108	28,999
30 to 89 days past due	104	170
90 days or more past due	48	67
Total past due	152	237
Total loans held for investment, excluding FDIC covered loans	29,260	29,236
Residential Mortgage [Member]
Aging of loans held for investment, excluding FDIC covered loans
Current	20,349	19,228
30 to 89 days past due	171	188
90 days or more past due	209	209
Total past due	380	397
Total loans held for investment, excluding FDIC covered loans	20,729	19,625
Home Equity and Other Consumer Loans [Member]
Aging of loans held for investment, excluding FDIC covered loans
Current	3,566	3,686
30 to 89 days past due	18	24
90 days or more past due	20	20
Total past due	38	44
Total loans held for investment, excluding FDIC covered loans	3,604	3,730
Consumer [Member]
Aging of loans held for investment, excluding FDIC covered loans
Current	23,915	22,914
30 to 89 days past due	189	212
90 days or more past due	299	229
Total past due	418	441
Total loans held for investment, excluding FDIC covered loans	$ 24,333	$ 23,355