Loans, Allowance for Credit Losses, and Credit Quality Consumer Loans by Credit Quality Indicator (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Consumer Loans by credit quality indicator [Abstract]
Home equity	$ 1,530,463	$ 1,636,058
Installment and credit cards	430,823	454,219
Residential mortgage	4,889,943	4,472,760
Total consumer	6,851,229	6,563,037
Performing Financing Receivable [Member]
Consumer Loans by credit quality indicator [Abstract]
Home equity	1,493,285	1,592,788
Installment and credit cards	427,918	450,698
Residential mortgage	4,812,794	4,397,271
Total consumer	6,733,997	6,440,757
30 To 89 Days Past Due [Member]
Consumer Loans by credit quality indicator [Abstract]
Home equity	8,739	10,583
Installment and credit cards	1,655	1,932
Residential mortgage	4,914	3,046
Total consumer	15,308	15,561
Potential Problem [Member]
Consumer Loans by credit quality indicator [Abstract]
Home equity	432	880
Installment and credit cards	0	2
Residential mortgage	5,341	3,781
Total consumer	5,773	4,663
Impaired [Member]
Consumer Loans by credit quality indicator [Abstract]
Home equity	28,007	31,807
Installment and credit cards	1,250	1,587
Residential mortgage	66,894	68,662
Total consumer	$ 96,151	$ 102,056