Short-Term Borrowings and Long-Term Debt (Narrative) (Details)	12 Months Ended
Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Debt Instrument [Line Items]
Long-term debt	$ 27,302,000	$ 40,370,000
Repayments of long-term debt	$ 10,000,000.0	$ 15,100,000
Number of long-term fixed-rate convertible advances repaid \| loan	2
Number of long-term fixed-rate advances added \| loan		5
Proceeds from Issuance of debt		$ 35,000,000.0
Early repayment of senior debt	$ 30,000,000.0
Debt prepayment fees	600,000
Debt conversion, original debt, amount	$ 300,000	$ 40,400,000
Percentage of Bank's long-term debt at fixed rate	1.00%	100.00%
Daily advances outstanding	$ 0	$ 0
Short-term advances	0	5,000,000.0
Fixed Rate Advance Matures in 2019
Debt Instrument [Line Items]
Repayments of long-term debt	15,100,000
Fixed Rate Advance Matures in 2020
Debt Instrument [Line Items]
Repayments of long-term debt		$ 10,000,000.0
Interest rate		1.85%
Fixed Rate Advance Matures in 2021
Debt Instrument [Line Items]
Repayments of long-term debt		$ 3,000,000.0
Interest rate		1.70%
Fixed Rate Advance Matures in 2022
Debt Instrument [Line Items]
Repayments of long-term debt		$ 2,000,000.0
Interest rate		1.69%
Fixed Rate Advance Matures in 2024
Debt Instrument [Line Items]
Repayments of long-term debt		$ 5,000,000.0
Interest rate		1.67%
Fixed Rate Convertible Advances, 0.79% and 0.43% Maturing in 2030
Debt Instrument [Line Items]
Proceeds from Issuance of debt	$ 27,000,000.0
Fixed Rate Convertible Advance, 0.79%, Maturing in 2030
Debt Instrument [Line Items]
Interest rate	0.79%
Fixed Rate Convertible Advance, 0.43% Maturing in 2030
Debt Instrument [Line Items]
Interest rate	0.43%
Fixed-Rate Convertible
Debt Instrument [Line Items]
Long-term debt	$ 27,000,000
Variable Convertible
Debt Instrument [Line Items]
Long-term debt	0
Letter of Credit
Debt Instrument [Line Items]
Line of credit facility, fair value of amount outstanding	43,000,000.0
Other Commercial Banks
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	32,000,000.0	$ 32,000,000.0
Credit Facility With Commercial Bank
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		40,000,000.0
Federal Home Loan Bank Borrowings
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	364,300,000	369,800,000
Security owned and pledged as collateral, fair value	542,600,000	578,700,000
FHLB lendable collateral	434,600,000	458,100,000
FHLB lendable pledged collateral	257,800,000	304,600,000
Line of credit facility, current borrowing capacity	187,500,000	216,300,000
Line of credit facility, fair value of amount outstanding	27,300,000	45,400,000
FHLB lendable unpledged collateral	176,800,000	153,500,000
Borrower in Custody \| Federal Reserve Bank Of Richmond
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	6,000,000.0	7,700,000
Borrower in Custody or Unsecured and Secured Commercial Lines
Debt Instrument [Line Items]
Amount outstanding	$ 0	0
Maximum
Debt Instrument [Line Items]
Initial period after which debt callable	10 years
Minimum
Debt Instrument [Line Items]
Initial period after which debt callable	3 months
Advances and Security Agreement
Debt Instrument [Line Items]
Percentage of assets limited to maximum borrowing capacity	30.00%
Line of credit facility, maximum borrowing capacity	$ 607,400,000	$ 538,800,000

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Debt, Short Term Advances

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Federal home loan bank lendable for the period.

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Federal home loan bank unpledged collateral for the period.

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Long-term Debt, Number of Long-term Fixed-rate Advances

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The amount of the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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The cash outflow for the extinguishment of long-term borrowing, with the highest claim on the assets of the entity in case of bankruptcy or liquidation, before its maturity.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

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Fair value of the amount outstanding under the credit facility.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

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Amount of cash outflow for cost from early extinguishment and prepayment of debt. Includes, but is not limited to, third-party cost, premium paid, and other fee paid to lender directly for debt extinguishment or debt prepayment. Excludes accrued interest.

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The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

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