Loan Portfolio and Credit Quality Troubled Debt Restructured Loans (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2018 Loans	Dec. 31, 2018 loan	Dec. 31, 2017 USD ($) Loans
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | Loans		5		1
Restructured Year to Date, Pre-modification recorded investment	$ 3,424			$ 108
Restructured Year to Date, Post-modification recorded investment	3,459			$ 109
TDRs that defaulted that were restructured in prior twelve months, Number of loans | Loans		1		0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	150			$ 0
Commercial and industrial
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans		3	3	0
Restructured Year to Date, Pre-modification recorded investment	1,249			$ 0
Restructured Year to Date, Post-modification recorded investment	1,249			$ 0
TDRs that defaulted that were restructured in prior twelve months, Number of loans | Loans		1		0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	150			$ 0
Commercial and industrial | Extension of Term
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			2
Restructured Year to Date, Post-modification recorded investment	250
Commercial and industrial | Temporary Rate Reduction
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Commercial and industrial | Payment Deferral
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Commercial and industrial | Combination of Concessions
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			1
Restructured Year to Date, Post-modification recorded investment	999
Commercial tax-exempt
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans		0	0	0
Restructured Year to Date, Pre-modification recorded investment	0			$ 0
Restructured Year to Date, Post-modification recorded investment	0			$ 0
TDRs that defaulted that were restructured in prior twelve months, Number of loans | Loans		0		0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	0			$ 0
Commercial tax-exempt | Extension of Term
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Commercial tax-exempt | Temporary Rate Reduction
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Commercial tax-exempt | Payment Deferral
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Commercial tax-exempt | Combination of Concessions
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Commercial real estate
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans		0	0	0
Restructured Year to Date, Pre-modification recorded investment	0			$ 0
Restructured Year to Date, Post-modification recorded investment	0			$ 0
TDRs that defaulted that were restructured in prior twelve months, Number of loans | Loans		0		0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	0			$ 0
Commercial real estate | Extension of Term
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Commercial real estate | Temporary Rate Reduction
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Commercial real estate | Payment Deferral
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Commercial real estate | Combination of Concessions
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Construction and land
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans		0	0	0
Restructured Year to Date, Pre-modification recorded investment	0			$ 0
Restructured Year to Date, Post-modification recorded investment	0			$ 0
TDRs that defaulted that were restructured in prior twelve months, Number of loans | Loans		0		0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	0			$ 0
Construction and land | Extension of Term
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Construction and land | Temporary Rate Reduction
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Construction and land | Payment Deferral
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Construction and land | Combination of Concessions
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Residential
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans		2	2	1
Restructured Year to Date, Pre-modification recorded investment	2,175			$ 108
Restructured Year to Date, Post-modification recorded investment	2,210			$ 109
TDRs that defaulted that were restructured in prior twelve months, Number of loans | Loans		0		0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	0			$ 0
Residential | Extension of Term
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Residential | Temporary Rate Reduction
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			2
Restructured Year to Date, Post-modification recorded investment	2,210
Residential | Payment Deferral
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Residential | Combination of Concessions
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Home equity
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans		0	0	0
Restructured Year to Date, Pre-modification recorded investment	0			$ 0
Restructured Year to Date, Post-modification recorded investment	0			$ 0
TDRs that defaulted that were restructured in prior twelve months, Number of loans | Loans		0		0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	0			$ 0
Home equity | Extension of Term
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Home equity | Temporary Rate Reduction
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Home equity | Payment Deferral
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Home equity | Combination of Concessions
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Consumer and other
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans		0	0	0
Restructured Year to Date, Pre-modification recorded investment	0			$ 0
Restructured Year to Date, Post-modification recorded investment	0			$ 0
TDRs that defaulted that were restructured in prior twelve months, Number of loans | Loans		0		0
TDRs that defaulted that were restructured in prior twelve months, Post-modification recorded investment	0			$ 0
Consumer and other | Extension of Term
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Consumer and other | Temporary Rate Reduction
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Consumer and other | Payment Deferral
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	0
Consumer and other | Combination of Concessions
Financing Receivable, Modifications [Line Items]
Restructured Year to Date, Number of Loans | loan			0
Restructured Year to Date, Post-modification recorded investment	$ 0