Loan Portfolio and Credit Quality Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 7,080,260	$ 6,893,158
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	656,186	623,037
Commercial tax-exempt
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	450,307	451,671
Total commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,106,493	1,074,708
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,530,556	2,395,692
Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	200,378	240,306
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,025,758	2,948,973
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	89,930	90,421
Consumer and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 127,145	$ 143,058