Loans and Credit Quality - Narrative (Details)	12 Months Ended
Dec. 31, 2020 USD ($) contract commitment loan	Dec. 31, 2019 USD ($) contract loan	Dec. 31, 2018 USD ($) contract
Accounts, Notes, Loans and Financing Receivable [Line Items]
PPP loans	$ 1,455,785,000	$ 1,048,456,000
Loans secured by real estate	73.00%
Loans unsecured	2.00%
Loans secured for general commercial uses	25.00%
Net nonaccrual loans	$ 9,599,000	13,951,000
Interest income earned on nonaccrual loans	856,000	1,300,000	$ 1,300,000
Interest income earned on nonaccrual loans with no balance	$ 924,000	$ 301,000	159,000
Number of loans past due greater than 90 days and still accruing interest \| loan	1	0
Recorded investment in loans considered to be impaired	$ 18,028,000	$ 24,673,000
Impaired loan, average recorded investment	20,982,000	28,395,000	34,700,000
Impaired loan, interest income on accrual method	333,000	623,000	$ 847,000
Loans classified as troubled debt restructuring	$ 7,860,000	10,100,000
Commitment to Lend \| commitment	0
Write down on TDR	$ 0	$ 64,000
TDR with specific impairment \| contract	1	0
TDR that subsequently defaulted, number of contracts \| contract	0	0	6
Unfunded loan commitments	$ 15,000	$ 15,000
Loans pledged as collateral	0	0
PPP Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned origination fees, net of origination costs	5,900,000
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
PPP loans	780,058,000	$ 412,690,000
Commercial \| PPP Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
PPP loans	$ 310,500,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recovery time for market	18 months
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recovery time for market	24 months

Financing Receivable, 90 Days or More Past Due, Still Accruing, Number Of Contracts

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- Definition

Financing Receivable, Modifications, Number of Commitments to Extend Financing

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Financing Receivable, Modifications with Specific Allowance, Number of Contracts

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Financing Receivable Recorded Investment Interest Income Earned On Nonaccrual Loans

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Financing Receivable, Recorded Investment, Nonaccrual Status, Excluding Government Guaranteed Payments

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- Definition

Financing Receivables Percentage Of Total Loans, Excluding PPP Loans, Secured By Real Estate

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Financing Receivables Percentage Of Total Loans, Excluding PPP Loans, Secured For General Commercial Uses

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Financing Receivables Percentage Of Total Loans, Excluding PPP Loans, Unsecured

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Financing receivables unfunded loan commitments to directors and officers.

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Interest Income Earned on Nonaccrual Loans With No Balance

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Recovery Time of Market

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of financing receivable modified as troubled debt restructuring.

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- Definition

Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

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Reflects the amount of the write-down related to a troubled debt restructuring.

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

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Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

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