Loan Portfolio and Credit Quality Nonaccrual Loans by Class of Financing Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual receivables	$ 14,057	$ 14,295
Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual receivables	2,554	748
Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual receivables	2,554	748
Commercial tax-exempt
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual receivables	0	0
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual receivables	546	1,985
Construction and land
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual receivables	0	110
Residential
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual receivables	7,914	8,470
Home equity
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual receivables	3,031	2,840
Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual receivables	$ 12	$ 142