Loan Portfolio and Credit Quality Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 5,751,497	$ 5,719,212
Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,042,917	1,111,555
Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,977,312	1,914,134
Construction and land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	142,549	183,434
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,280,116	2,229,540
Home equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	125,486	119,828
Consumer and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 183,117	$ 160,721