Stock-Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity Incentive Plan, shares authorized	1,500,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 2,204
Total unrecognized compensation expense, weighted average period	11 months 26 days
Vesting period	3 years
Granted, Shares	35,002
Outstanding, Shares	121,462	99,724
Fair value of granted shares per share	$ 49.02
Performance-based restricted shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Granted, Shares	36,403
Performance-based restricted shares [Member] \| February 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Shares	30,057
Percentage of target opportunity for awards to vest	120.00%
Fair value of granted shares per share	$ 49.33
Expense incurred to grant shares	$ 595
Expiry period	3 years
Maturity date	Dec. 31, 2019
Performance-based restricted shares [Member] \| February 2017 [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target opportunity for awards to vest	0.00%
Performance-based restricted shares [Member] \| February 2017 [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target opportunity for awards to vest	150.00%
Performance-based restricted shares [Member] \| February and July 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Shares	35,258
Percentage of target opportunity for awards to vest	117.00%
Fair value of granted shares per share	$ 49.04
Expense incurred to grant shares	$ 674
Expiry period	3 years
Maturity date	Dec. 31, 2020
Performance-based restricted shares [Member] \| February and July 2018 [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target opportunity for awards to vest	0.00%
Performance-based restricted shares [Member] \| February and July 2018 [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target opportunity for awards to vest	150.00%
Performance-based restricted shares [Member] \| February 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Shares	36,403
Percentage of target opportunity for awards to vest	108.00%
Fair value of granted shares per share	$ 49.10
Expense incurred to grant shares	$ 590
Expiry period	3 years
Maturity date	Dec. 31, 2021
Performance-based restricted shares [Member] \| February 2019 [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target opportunity for awards to vest	0.00%
Performance-based restricted shares [Member] \| February 2019 [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target opportunity for awards to vest	150.00%
SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Shares	0
Outstanding, Shares		237,121

Percentage of target opportunity for awards to vest.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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The cash outflow for cost incurred directly with the issuance of an equity security.

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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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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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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Number of options outstanding, including both vested and non-vested options.

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