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Employee Share-Based Compensation Plans - Summary Weighted-average Fair Value of the Shares Issued Under the ESPP Plans (Detail)
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12 Months Ended | ||
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Expected volatility | 47.50% | 52.40% | 53.80% |
| Expected dividend yield | |||
| Expected life (in years) | 3 years 9 months | 3 years 10 months 10 days | 3 years 7 months 10 days |
| Risk-free interest rate | 0.40% | 0.40% | 1.10% |
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Employee Stock Purchase Plan [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Expected volatility | 42.70% | 52.50% | 53.40% |
| Expected dividend yield | |||
| Expected life (in years) | 3 months | 3 months | 3 months |
| Risk-free interest rate | 0.10% | 0.10% | 0.10% |