Loan Portfolio and Credit Quality Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	$ 7,043,338	$ 6,976,704
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	670,744	694,034
Commercial tax-exempt
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	445,319	447,927
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	2,626,299	2,551,274
Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	238,293	225,983
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	2,841,926	2,839,155
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	89,350	83,657
Consumer and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	$ 131,407	$ 134,674