Loans, Allowance for Loan Losses, and Credit Quality (Details 5) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Consumer Loans By Credit Quality Indicator [Abstract]
Home equity	$ 2,501,770	$ 2,504,704
Installment	537,628	557,782
Total retail	3,039,398	3,062,486
Residential mortgage	3,129,144	2,951,013
Total consumer	6,168,542	6,013,499
Performing [member]
Consumer Loans By Credit Quality Indicator [Abstract]
Home equity	2,425,602	2,431,207
Installment	531,047	551,227
Total retail	2,956,649	2,982,434
Residential mortgage	3,026,225	2,849,082
Total consumer	5,982,874	5,831,516
30-89 Days Past Due [Member]
Consumer Loans By Credit Quality Indicator [Abstract]
Home equity	18,007	12,189
Installment	2,813	2,592
Total retail	20,820	14,781
Residential mortgage	10,114	7,224
Total consumer	30,934	22,005
Potential Problem [Member]
Consumer Loans By Credit Quality Indicator [Abstract]
Home equity	4,441	5,451
Installment	142	233
Total retail	4,583	5,684
Residential mortgage	9,580	13,037
Total consumer	14,163	18,721
Impaired [Member]
Consumer Loans By Credit Quality Indicator [Abstract]
Home equity	53,720	55,857
Installment	3,626	3,730
Total retail	57,346	59,587
Residential mortgage	83,225	81,670
Total consumer	$ 140,571	$ 141,257