Stock-Based Compensation Plan (Restricted Stock Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, authorized common stock	500,000
Shares, Nonvested, beginning of period	16,701	14,401
Shares, Granted	22,488	16,950
Shares, Vested	(12,400)	(9,109)
Shares, Forfeited	0	(41)
Shares, Nonvested, end of period	26,789	22,201
Weighted Average Grant Date Fair Value, Nonvested, beginning of period	$ 29.72	$ 24.68
Weighted Average Grant Date Fair Value, Granted	30.69	32.84
Weighted Average Grant Date Fair Value, Vested	29.54	24.63
Weighted average Grant Date Fair Value, Forfeited	0.00	25.50
Weighted Average Grant Date Fair Value, Nonvested, end of period	$ 30.62	$ 30.93
Deferred Compensation Arrangements Unrecognized Compensation Cost Related To Unvested Restricted Stock	$ 227
Outside Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting service period of grants to executive officers	9 months
Service Period [Member] \| Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting service period of grants to executive officers	3 years
Performance Measure [Member] \| Executive Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting service period of grants to executive officers	1 year

Deferred Compensation Arrangements Unrecognized Compensation Cost Related To Unvested Restricted Stock

No definition available.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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- Definition

Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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- Definition

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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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

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- Definition

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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