Loans, Allowance for Credit Losses, and Credit Quality Consumer Loans by Credit Quality Indicator (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Consumer Loans by credit quality indicator [Abstract]
Home equity	$ 1,583,614	$ 1,636,058
Installment and credit cards	436,492	454,219
Residential mortgage	4,658,574	4,472,760
Total consumer	6,678,680	6,563,037
Performing Financing Receivable [Member]
Consumer Loans by credit quality indicator [Abstract]
Home equity	1,542,482	1,592,788
Installment and credit cards	433,268	450,698
Residential mortgage	4,581,063	4,397,271
Total consumer	6,556,813	6,440,757
30 To 89 Days Past Due [Member]
Consumer Loans by credit quality indicator [Abstract]
Home equity	10,008	10,583
Installment and credit cards	1,818	1,932
Residential mortgage	3,403	3,046
Total consumer	15,229	15,561
Potential Problem [Member]
Consumer Loans by credit quality indicator [Abstract]
Home equity	958	880
Installment and credit cards	0	2
Residential mortgage	6,621	3,781
Total consumer	7,579	4,663
Impaired [Member]
Consumer Loans by credit quality indicator [Abstract]
Home equity	30,166	31,807
Installment and credit cards	1,406	1,587
Residential mortgage	67,487	68,662
Total consumer	$ 99,059	$ 102,056