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Stock Incentive and Employee Stock Purchase Plans - Summary of per Share Fair Values of Stock Options Granted under 2009 Plan and Rights Granted under ESPP (Detail)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Employee Stock Options [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected dividend yield 0.00% 0.00% 0.00%
Risk-free interest rate 0.80% 0.90% 1.20%
Volatility 63.00% 63.00% 69.00%
Expected term (in years) 6 years 6 years 6 years
Employee Stock Purchase Rights [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected dividend yield 0.00% 0.00% 0.00%
Risk-free interest rate 0.00% 0.20% 0.20%
Volatility 0.00% 68.00% 63.00%
Expected term (in years) 0 years 1 year 3 months 18 days 1 year 1 month 6 days