Share-based Compensation - Summary of Information under Plans (Detail) - USD ($) $ / shares in Units, $ in Thousands |
12 Months Ended | ||
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Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||
| Grant date fair value of options granted | $ 0 | $ 0 | $ 78 |
| Fair value of options vested | 820 | 2,322 | 2,668 |
| Total intrinsic value of options exercised | 432 | 1,862 | 488 |
| Proceeds from exercise of stock options | $ 288 | $ 1,453 | $ 616 |
| Weighted-average estimated fair value per share of options granted (in usd per share) | $ 0.00 | $ 0.00 | $ 3.62 |
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- Definition Share Based Compensation Arrangement By Share Based Payment Award Awards Granted During Period Aggregate Fair Value No definition available.
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- Definition Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value Per Share No definition available.
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- References No definition available.
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- Definition Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition 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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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