Loans, Allowance for Credit Losses and Credit Quality Finance Receivable, Nonaccrual (Details) - USD ($) $ in Thousands	Mar. 31, 2021		Dec. 31, 2020
Financing Receivable, Nonaccrual [Line Items]
Finance Receivable, Nonaccrual, with allowance	$ 28,499		$ 31,332
Financing Receivable, Nonaccrual, No Allowance	30,701		35,528
Tdrs Recorded Investment On Nonaccrual Status	21,167		22,209
Financing Receivable Recorded Investment Trouble Debt Restructuring	41,429		39,192
Additional Commitments To Lend To Borrower For Trouble Debt Restructuring	466		263
Financing Receivable, Nonaccrual	59,200	[1]	66,860
Tdrs Recorded Investment On Accrual Status	20,262		16,983
Commercial And Industrial [Member]
Financing Receivable, Nonaccrual [Line Items]
Finance Receivable, Nonaccrual, with allowance	3,606		3,804
Financing Receivable, Nonaccrual, No Allowance	26,179		30,925
Financing Receivable, Nonaccrual	29,785		34,729
Commercial Real Estate [Member]
Financing Receivable, Nonaccrual [Line Items]
Finance Receivable, Nonaccrual, with allowance	9,635		10,195
Financing Receivable, Nonaccrual	9,635		10,195
Small Business [Member]
Financing Receivable, Nonaccrual [Line Items]
Finance Receivable, Nonaccrual, with allowance	660		815
Financing Receivable, Nonaccrual, No Allowance			10
Financing Receivable, Nonaccrual	660		825
Residential Real Estate [Member]
Financing Receivable, Nonaccrual [Line Items]
Finance Receivable, Nonaccrual, with allowance	8,870		10,935
Financing Receivable, Nonaccrual, No Allowance	4,522		4,593
Financing Receivable, Nonaccrual	13,392		15,528
Home Equity Line of Credit [Member]
Financing Receivable, Nonaccrual [Line Items]
Finance Receivable, Nonaccrual, with allowance	5,592		5,427
Financing Receivable, Nonaccrual	5,592		5,427
Consumer - Other [Member]
Financing Receivable, Nonaccrual [Line Items]
Finance Receivable, Nonaccrual, with allowance	136		156
Financing Receivable, Nonaccrual	$ 136		$ 156

[1] Included in these amounts were $21.2 million and $22.2 million of nonaccruing TDRs at March 31, 2021 and December 31, 2020, respectively.