Loans, Allowance for Credit Losses, and Credit Quality Troubled Debt Restructurings Performing and Nonaccrual (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	$ 82,809	$ 98,216
Nonaccrual Restructured Loans	36,583	57,656
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	28,598	33,892
Nonaccrual Restructured Loans	1,946	3,260
Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	7,343	10,454
Nonaccrual Restructured Loans	2,796	5,656
Commercial Real Estate Investor [Member]
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	18,580	23,127
Nonaccrual Restructured Loans	4,268	15,216
Real Estate Construction [Member]
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	485	727
Nonaccrual Restructured Loans	173	2,438
Home Equity Portfolio [Member]
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	6,945	8,209
Nonaccrual Restructured Loans	4,137	4,838
Installment and Credit Cards [Member]
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	804	974
Nonaccrual Restructured Loans	65	199
Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	20,054	20,833
Nonaccrual Restructured Loans	$ 23,198	$ 26,049