Loan Portfolio and Credit Quality Loans Restructured (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) loan	Jun. 30, 2018 USD ($) loan	Jun. 30, 2019 USD ($) loan	Jun. 30, 2018 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan	2		4
Restructuring Current Quarter, Pre-modification recorded investment	$ 496		$ 3,675
Restructuring Current Quarter, Post-modification recorded investment	$ 496		$ 3,675
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Number of Loans | loan	0		0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Post-modification recorded investment	$ 0		$ 0
Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan	0	1	1	1
Restructuring Current Quarter, Pre-modification recorded investment	$ 0	$ 100	$ 179	$ 100
Restructuring Current Quarter, Post-modification recorded investment	$ 0	$ 100	$ 179	$ 100
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Commercial tax-exempt
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan	0	0	0	0
Restructuring Current Quarter, Pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Restructuring Current Quarter, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan	0	0	0	0
Restructuring Current Quarter, Pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Restructuring Current Quarter, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Construction and land
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan	0	0	0	0
Restructuring Current Quarter, Pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Restructuring Current Quarter, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan	1	0	2	0
Restructuring Current Quarter, Pre-modification recorded investment	$ 222	$ 0	$ 3,222	$ 0
Restructuring Current Quarter, Post-modification recorded investment	$ 222	$ 0	$ 3,222	$ 0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan	1	0	1	0
Restructuring Current Quarter, Pre-modification recorded investment	$ 274	$ 0	$ 274	$ 0
Restructuring Current Quarter, Post-modification recorded investment	$ 274	$ 0	$ 274	$ 0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Consumer and other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan	0	0	0	1
Restructuring Current Quarter, Pre-modification recorded investment	$ 0	$ 0	$ 0	$ 100
Restructuring Current Quarter, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 100
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted in the Current Quarter that were restructured in prior twelve months, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Extension of term | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			1
Restructuring Current Quarter, Post-modification recorded investment			$ 179
Extension of term | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Extension of term | Construction and land
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Extension of term | Residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Extension of term | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Extension of term | Consumer and other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Temporary rate reduction | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Temporary rate reduction | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Temporary rate reduction | Construction and land
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Temporary rate reduction | Residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			2
Restructuring Current Quarter, Post-modification recorded investment			$ 3,222
Temporary rate reduction | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			1
Restructuring Current Quarter, Post-modification recorded investment			$ 274
Temporary rate reduction | Consumer and other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Payment deferral | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Payment deferral | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Payment deferral | Construction and land
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Payment deferral | Residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Payment deferral | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Payment deferral | Consumer and other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Combination Of Concessions | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Combination Of Concessions | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Combination Of Concessions | Construction and land
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Combination Of Concessions | Residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Combination Of Concessions | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0
Combination Of Concessions | Consumer and other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring Current Quarter, Number of Loans | loan			0
Restructuring Current Quarter, Post-modification recorded investment			$ 0