Stock-Based Compensation (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred income tax expense (benefit)	$ (313)	$ (1,761)	$ (1,096)
Proceeds from issuance of common stock	$ 100	$ 100	$ 100
Number of stock options settled for fully vested shares	55,050	30,700	104,000
Number of shares issued in settlement of stock option	13,482	9,976	46,432
Intrinsic value of stock options exercised	$ 700	$ 500	$ 2,300
Income tax benefits	$ 6,798	9,787	10,834
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	55,350
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred income tax expense (benefit)	$ 1,200	1,200	1,100
Equity Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Income tax benefits	$ 100	100	800
2011 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized	1,355,764
Shares reserved for future issuance	605,788
Number of outstanding awards	340,302
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 2,200
Weighted average remaining service period of nonvested awards	2 years 20 days
Vesting term	5 years
Total intrinsic value of vested RSU's	$ 2,700	$ 1,800	$ 2,000
Performance-based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 1,300
Weighted average remaining service period of nonvested awards	1 year 11 months 18 days

Number of shares issued in settlement of stock option.

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Number of stock options settled for fully vested shares.

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Aggregate number of common shares reserved for future issuance.

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Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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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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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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