Quarterly report pursuant to Section 13 or 15(d)

Summary of Unvested Stock Option Activity (Detail)

v3.8.0.1
Summary of Unvested Stock Option Activity (Detail) - $ / shares
shares in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Weighted Average Grant Date Fair Value    
Granted $ 0.29 $ 1.05
Stock Options    
Shares    
Beginning Balance 3,283  
Granted 2,519  
Vested (630)  
Forfeited or cancelled (38)  
Ending Balance 5,134  
Weighted Average Grant Date Fair Value    
Beginning Balance $ 0.95  
Granted 0.29  
Vested 0.83  
Forfeited or cancelled 1.19  
Ending Balance $ 0.69