Stock-Based Compensation (Options Outstanding) (Details) - $ / shares	3 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	4,150	4,500
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 22.91	$ 22.91
Options Exercised, Shares	(350)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 22.91

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

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-Topic 718
-SubTopic 10
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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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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 share options (or share units) exercised during the current period.

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