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Stockholders' Equity - Summary of Weighted Average Assumptions Used to Estimate Fair Value of Stock Option (Detail) (Stock Options [Member], USD $)
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3 Months Ended | |
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Mar. 31, 2015
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Mar. 31, 2014
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Stock Options [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Expected option term (in years) | 6 years | 5 years |
| Risk-free interest rate | 1.60% | 1.50% |
| Expected volatility | 43.00% | 45.00% |
| Expected dividend yield | 0.00% | 0.00% |
| Weighted average exercise price | $ 30.76 | $ 23.00 |
| Weighted average fair value at grant date | $ 13.25 | $ 9.40 |