Stock-Based Compensation (Details Textual) $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2018 USD ($) $ / shares shares
Other information
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period \| shares	87,557
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price \| $ / shares	$ 21.55
Restricted Awards [Member]
Other information
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period \| shares	86,870
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value \| $ / shares	$ 29.40
Restricted Awards [Member] \| Long-Term Incentive Plan [Member]
Weighted-Average Grant Date Fair Value
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value \| $ / shares	$ 30.16
Other information
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period \| shares	92,244
Performance awards [Member]
Other information
Reversal of Share Based Compensation \| $	$ 0.4
Performance awards [Member] \| Maximum [Member]
Weighted-Average Grant Date Fair Value
Potential Payout As a Percentage of Target Shares	200.00%
Performance awards [Member] \| Long-Term Incentive Plan [Member]
Weighted-Average Grant Date Fair Value
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value \| $ / shares	$ 34.52
Other information
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period \| shares	66,764
Market based Performance Awards [Member]
Other information
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period	2 years 9 months 18 days
Internal Measure based Performance Awards [Member]
Other information
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period	2 years 9 months 18 days
Restricted Stock Units (RSUs) [Member]
Other information
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period	1 year

No definition available.

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The aggregate amount of noncash, equity-based employee remuneration which is reversed during the period.

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The percentage of target shares, an employee can earn, under the plan.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, 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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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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

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

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