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Share-based Compensation - Additional Information (Detail) (USD $)
Share data in Millions, except Per Share data, unless otherwise specified |
3 Months Ended |
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Mar. 31, 2015
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Share available for future grants | 2.5 |
| Stock options contractual terms | 8 years 1 month 10 days |
| Aggregate intrinsic value of options exercised | $ 23,000 |
| Weighted average fair value of stock options granted | $ 8.42 |
| Fair value of share-awards vested | 1,000,000 |
| Stock options | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Unrecognized compensation cost | 10,100,000 |
| Weighted average recognition period (years) | 1 year 8 months 12 days |
| Nonvested share-awards | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Unrecognized compensation cost | $ 9,900,000 |
| Weighted average recognition period (years) | 2 years 7 months 6 days |