Loans and Allowance for Loan Losses (Details 5) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Aging of loans
Current	$ 71,201	$ 66,785
30 to 89 Days Past Due	268	285
90 Days or More Past Due	116	136
Total Past Due	384	421
Total loans held for investment, before purchased credit-impaired loans	71,585	67,206
Total loans 90 days or more past due and still accruing	11	5
Commercial portfolio
Aging of loans
Current	40,638	38,205
30 to 89 Days Past Due	131	148
90 Days or More Past Due	19	26
Total Past Due	150	174
Total loans held for investment, before purchased credit-impaired loans	40,788	38,379
Commercial portfolio | Commercial and industrial
Aging of loans
Current	25,946	24,310
30 to 89 Days Past Due	33	66
90 Days or More Past Due	12	6
Total Past Due	45	72
Total loans held for investment, before purchased credit-impaired loans	25,991	24,382
Commercial portfolio | Commercial mortgage
Aging of loans
Current	13,444	13,004
30 to 89 Days Past Due	98	68
90 Days or More Past Due	7	20
Total Past Due	105	88
Total loans held for investment, before purchased credit-impaired loans	13,549	13,092
Commercial portfolio | Construction
Aging of loans
Current	1,248	891
30 to 89 Days Past Due		14
Total Past Due		14
Total loans held for investment, before purchased credit-impaired loans	1,248	905
Consumer portfolio
Aging of loans
Current	30,563	28,580
30 to 89 Days Past Due	137	137
90 Days or More Past Due	97	110
Total Past Due	234	247
Total loans held for investment, before purchased credit-impaired loans	30,797	28,827
Consumer portfolio | Residential mortgage
Aging of loans
Current	27,419	25,342
30 to 89 Days Past Due	120	114
90 Days or More Past Due	80	91
Total Past Due	200	205
Total loans held for investment, before purchased credit-impaired loans	27,619	25,547
Consumer portfolio | Home equity and other consumer loans
Aging of loans
Current	3,144	3,238
30 to 89 Days Past Due	17	23
90 Days or More Past Due	17	19
Total Past Due	34	42
Total loans held for investment, before purchased credit-impaired loans	3,178	3,280
Purchased credit-impaired loans
Aging of loans
Total loans 90 days or more past due and still accruing	$ 103	$ 124