Loans, Allowance for Credit Losses and Credit Quality Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) contract	Jun. 30, 2019 USD ($) contract	Jun. 30, 2020 USD ($) contract	Jun. 30, 2019 USD ($) contract	Dec. 31, 2019 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	7	3	12	5
Tdrs Recorded Investment On Accrual Status	$ 17,741		$ 17,741		$ 19,599
Tdrs Recorded Investment On Nonaccrual Status	24,098		24,098		24,766
Financing Receivable Recorded Investment Trouble Debt Restructuring	41,839		41,839		44,365
Amount Of Specific Reserves Included In Allowance For Loan Losses Associated With Trouble Debt Restructuring					855
Additional Commitments To Lend To Borrower For Trouble Debt Restructuring	139		139		$ 63
Financing Receivable, Troubled Debt Restructuring, Premodification	1,655	$ 153	2,753	$ 378
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 1,706	$ 153	$ 2,812	$ 378
Commercial And Industrial [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	1	1	3	1
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 40	$ 97	$ 308	$ 97
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 40	$ 97	$ 308	$ 97
Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	4	0	5	1
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 1,170		$ 1,774	$ 150
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 1,170		$ 1,774	$ 150
Small Business [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	1	2	2	2
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 63	$ 56	$ 112	$ 56
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 63	$ 56	$ 88	$ 56
Residential Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	1		2
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 382		$ 559
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 433		$ 642
Home Equity Line of Credit [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	0	0	0	1
Financing Receivable, Troubled Debt Restructuring, Premodification				$ 75
Financing Receivable, Troubled Debt Restructuring, Postmodification				$ 75
Consumer Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	0		0