Loan Portfolio and Credit Quality - Loans Restructured (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 USD ($) loan	Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | loan	0	2	2	4
Restructuring current quarter, pre-modification recorded investment	$ 0	$ 496	$ 2,423	$ 3,675
Restructuring Current Quarter, Post-modification recorded investment	$ 0	$ 496	$ 2,423	$ 3,675
TDRs that defaulted that were restructured in prior twelve months, Number of Loans | loan	1	0	1	0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	$ 1,562	$ 0	$ 1,562	$ 0
Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | loan	0	0	1	1
Restructuring current quarter, pre-modification recorded investment	$ 0	$ 0	$ 50	$ 179
Restructuring Current Quarter, Post-modification recorded investment	$ 0	$ 0	$ 50	$ 179
TDRs that defaulted that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Paycheck Protection Program
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | loan	0		0
Restructuring current quarter, pre-modification recorded investment	$ 0		$ 0
Restructuring Current Quarter, Post-modification recorded investment	$ 0		$ 0
TDRs that defaulted that were restructured in prior twelve months, Number of Loans | loan	0		0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	$ 0		$ 0
Commercial tax-exempt
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | 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 that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted 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 processed | 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 that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted 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 processed | 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 that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted 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 processed | loan	0	1	1	2
Restructuring current quarter, pre-modification recorded investment	$ 0	$ 222	$ 2,373	$ 3,222
Restructuring Current Quarter, Post-modification recorded investment	$ 0	$ 222	$ 2,373	$ 3,222
TDRs that defaulted that were restructured in prior twelve months, Number of Loans | loan	1	0	1	0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	$ 1,562	$ 0	$ 1,562	$ 0
Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | loan	0	1	0	1
Restructuring current quarter, pre-modification recorded investment	$ 0	$ 274	$ 0	$ 274
Restructuring Current Quarter, Post-modification recorded investment	$ 0	$ 274	$ 0	$ 274
TDRs that defaulted that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted 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 processed | 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 that were restructured in prior twelve months, Number of Loans | loan	0	0	0	0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Extension of term
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | loan				1
Restructuring Current Quarter, Post-modification recorded investment				$ 179
Extension of term | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | loan				1
Restructuring Current Quarter, Post-modification recorded investment				$ 179
Extension of term | Commercial tax-exempt
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | loan				0
Restructuring Current Quarter, Post-modification recorded investment				$ 0
Extension of term | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | 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 processed | 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 processed | 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 processed | 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 processed | loan				0
Restructuring Current Quarter, Post-modification recorded investment				$ 0
Temporary rate reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | loan				3
Restructuring Current Quarter, Post-modification recorded investment				$ 3,496
Temporary rate reduction | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | loan				0
Restructuring Current Quarter, Post-modification recorded investment				$ 0
Temporary rate reduction | Commercial tax-exempt
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | 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 processed | 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 processed | 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 processed | 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 processed | 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 processed | loan				0
Restructuring Current Quarter, Post-modification recorded investment				$ 0
Payment deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | 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 processed | loan				0
Restructuring Current Quarter, Post-modification recorded investment				$ 0
Payment deferral | Commercial tax-exempt
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | 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 processed | 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 processed | 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 processed | 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 processed | 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 processed | loan				0
Restructuring Current Quarter, Post-modification recorded investment				$ 0
Combination of concessions
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | 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 processed | loan				0
Restructuring Current Quarter, Post-modification recorded investment				$ 0
Combination of concessions | Commercial tax-exempt
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructuring current quarter, number of loans processed | 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 processed | 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 processed | 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 processed | 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 processed | 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 processed | loan				0
Restructuring Current Quarter, Post-modification recorded investment				$ 0