Loan Portfolio and Credit Quality - Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 7,216,325	$ 7,104,309
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	668,217	558,343
Paycheck Protection Program
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	351,170	312,356
Commercial tax-exempt
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	488,507	442,159
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,697,677	2,757,375
Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	181,482	159,204
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,632,554	2,677,464
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	71,752	77,364
Consumer and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 124,966	$ 120,044