| **Share-Based Compensation - Stock Option Activity under Stock Option Plans (Details) (USD $)** | 6 Months Ended            |
|-------------------------------------------------------------------------------------------------|---------------------------|
||
| **Number of Shares**                                                                            |                      |
| Beginning balance (in shares)                                                                   | 958,786                   |
| Granted (in shares)                                                                             |                 |
| Exercised (in shares)                                                                           | (38,650)                  |
| Cancelled (in shares)                                                                           | (68,707)                  |
| Ending balance (in shares)                                                                      | 851,429                   |
| Vested and Expected to Vest (in shares)                                                         | 851,429                   |
| Exercisable (in shares)                                                                         | 842,429                   |
| **Weighted-Average Exercise Price**                                                             |                      |
| Beginning balance (in dollars per share)                                                        | $ 21.32                   |
| Granted (in dollars per share)                                                                  |                 |
| Exercised (in dollars per share)                                                                | $ 11.64                   |
| Cancelled (in dollars per share)                                                                | $ 22.55                   |
| Ending balance (in dollars per share)                                                           | $ 21.65                   |
| Vested and Expected to Vest (in dollars per share)                                              | $ 21.65                   |
| Exercisable (in dollars per share)                                                              | $ 21.72                   |
| **Weighted Average Remaining Contractual Term**                                                 |                      |
| Outstanding                                                                                     | 3 years 5 months 16 days  |
| Vested and Expected to Vest                                                                     | 2 years 11 months 12 days |
| Exercisable                                                                                     | 3 years 4 months 21 days  |
| **Aggregate Intrinsic Value**                                                                   |                      |
| Outstanding                                                                                     | $ 2,149,732               |
| Vested and Expected to Vest                                                                     | 2,149,732                 |
| Exercisable                                                                                     | $ 2,097,352               |

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| - Definition
Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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| - Definition
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.
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| - Definition
Gross number of share options (or share units) granted during the period.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of options outstanding, including both vested and non-vested options.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.
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| - Definition
Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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| - Definition
Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.
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| - Definition
As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.
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| - Definition
As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.
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| - Definition
Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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| - Definition
Weighted average price at which option holders acquired shares when converting their stock options into shares.
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| - Definition
Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.
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| - Definition
Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.
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| - Definition
Number of share options (or share units) exercised during the current period.
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