Loans Receivable and Credit Quality Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 6,114,354	$ 5,719,212
Commercial and Industrial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,009,974	964,786
Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	611,370	633,019
Commercial Tax Exempt [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	398,604	331,767
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,302,244	2,060,903
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	104,839	183,434
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,379,861	2,229,540
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	118,817	119,828
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 198,619	$ 160,721