Share-Based Compensation - Summary of Stock Option Activity (Details) - 6 months ended Jun. 30, 2015 - $ / shares	Total
Summary of stock option activity
Options outstanding, Beginning Balance, Shares	247,590
Exercised, Shares	(47,029)
Forfeited or Expired, Shares	(129,741)
Options outstanding, Ending Balance, Shares	70,820
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options outstanding, Beginning Balance, Weighted Average Exercise Price	$ 17.82
Exercised, Weighted Average Exercise Price	16.62
Forfeited or Expired, Weighted Average Exercise Price	18.91
Options outstanding, Ending Balance, Weighted Average Exercise Price	$ 16.62
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options outstanding, Beginning Balance, Options Exercisable	247,590
Options outstanding, Ending Balance, Options Exercisable	70,820

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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For presentations that combine terminations, 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 or that expired.

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Weighted average price of options that were either forfeited or expired.

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- Definition

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

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

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