Loans and Allowance for Loan Losses (Details 11) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Information about impaired loans by class
Impaired loans	$ 569	$ 572
Allowance for impaired loans	43	69
Average balance	560	567
With Allowance [Member]
Information about impaired loans by class
Impaired loans	362	380
Unpaid principal balance	395	414
Without Allowance [Member]
Information about impaired loans by class
Impaired loans	207	192
Unpaid principal balance	242	229
Commercial and Industrial [Member]
Information about impaired loans by class
Impaired loans	218	220
Allowance for impaired loans	22	46
Average balance	205	185
Commercial and Industrial [Member] | With Allowance [Member]
Information about impaired loans by class
Impaired loans	156	182
Unpaid principal balance	167	191
Commercial and Industrial [Member] | Without Allowance [Member]
Information about impaired loans by class
Impaired loans	62	38
Unpaid principal balance	62	40
Commercial Mortgage [Member]
Information about impaired loans by class
Impaired loans	116	130
Allowance for impaired loans	2	2
Average balance	121	191
Commercial Mortgage [Member] | With Allowance [Member]
Information about impaired loans by class
Impaired loans	18	27
Unpaid principal balance	29	39
Commercial Mortgage [Member] | Without Allowance [Member]
Information about impaired loans by class
Impaired loans	98	103
Unpaid principal balance	120	124
Construction Loans [Member]
Information about impaired loans by class
Impaired loans	40	66
Allowance for impaired loans		6
Average balance	57	56
Construction Loans [Member] | With Allowance [Member]
Information about impaired loans by class
Impaired loans		26
Unpaid principal balance	1	29
Construction Loans [Member] | Without Allowance [Member]
Information about impaired loans by class
Impaired loans	40	40
Unpaid principal balance	43	43
Commercial [Member]
Information about impaired loans by class
Impaired loans	374	416
Allowance for impaired loans	24	54
Average balance	383	432
Commercial [Member] | With Allowance [Member]
Information about impaired loans by class
Impaired loans	174	235
Unpaid principal balance	197	259
Commercial [Member] | Without Allowance [Member]
Information about impaired loans by class
Impaired loans	200	181
Unpaid principal balance	225	207
Residential Mortgage [Member]
Information about impaired loans by class
Impaired loans	185	142
Allowance for impaired loans	19	14
Average balance	164	117
Residential Mortgage [Member] | With Allowance [Member]
Information about impaired loans by class
Impaired loans	185	142
Unpaid principal balance	195	148
Home Equity and Other Consumer Loans [Member]
Information about impaired loans by class
Impaired loans	2	2
Average balance	2	2
Home Equity and Other Consumer Loans [Member] | With Allowance [Member]
Information about impaired loans by class
Impaired loans	2	2
Unpaid principal balance	2	2
Consumer [Member]
Information about impaired loans by class
Impaired loans	187	144
Allowance for impaired loans	19	14
Average balance	166	119
Consumer [Member] | With Allowance [Member]
Information about impaired loans by class
Impaired loans	187	144
Unpaid principal balance	197	150
Impaired Loans Excluding FDIC Covered Loans [Member]
Information about impaired loans by class
Impaired loans	561	560
Allowance for impaired loans	43	68
Average balance	549	551
Impaired Loans Excluding FDIC Covered Loans [Member] | With Allowance [Member]
Information about impaired loans by class
Impaired loans	361	379
Unpaid principal balance	394	409
Impaired Loans Excluding FDIC Covered Loans [Member] | Without Allowance [Member]
Information about impaired loans by class
Impaired loans	200	181
Unpaid principal balance	225	207
Covered Loans [Member]
Information about impaired loans by class
Impaired loans	8	12
Allowance for impaired loans		1
Average balance	11	16
Covered Loans [Member] | With Allowance [Member]
Information about impaired loans by class
Impaired loans	1	1
Unpaid principal balance	1	5
Covered Loans [Member] | Without Allowance [Member]
Information about impaired loans by class
Impaired loans	7	11
Unpaid principal balance	$ 17	$ 22