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Fair Value-Based Measurements and Weighted-Average Assumptions (Detail) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Employee Stock Purchase Plan
     
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Weighted-average fair value $ 0.93 $ 3.54 $ 2.09
Risk-free interest rate 0.20% 0.20% 0.30%
Expected life (in year) 1 year 3 months 18 days 1 year 1 month 6 days 1 year 2 months 12 days
Volatility 0.80% 1.60% 1.60%
Stock Options
     
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Weighted-average fair value $ 2.41 $ 3.30 $ 2.76
Risk-free interest rate 1.10% 0.50% 1.30%
Expected life (in year) 5 years 10 months 24 days 4 years 2 months 12 days 4 years
Volatility 1.40% 1.60% 1.60%