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Stock-Based Compensation - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total compensation cost related to unvested stock options and RSU $ 18,300,000    
Weighted-average period of unvested stock options and RSU 2 years 11 months 9 days    
Capitalized stock-based employee compensation expense $ 0    
Weighted-average estimated fair value per share of options granted $ 5.72 $ 8.16 $ 8.29
Issuance of common stock under employee stock purchase plan, shares 128,181 107,203 180,551
Stock issued under employee stock purchase plans, average exercise price $ 7.10 $ 7.92 $ 2.75
Weighted-average estimated fair value of shares purchased under ESPP plan $ 4.42 $ 3.25 $ 1.47
Restricted Stock Units (RSUs) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total compensation cost related to unvested stock options and RSU $ 8,100,000    
Weighted-average period of unvested stock options and RSU 2 years 4 months 2 days