Quarterly report pursuant to Section 13 or 15(d)

Description of Stock Plans - Summary of Options Granted Under All Equity Plans (Detail)

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Description of Stock Plans - Summary of Options Granted Under All Equity Plans (Detail) - Stock Option - USD ($)
$ / shares in Units, $ in Thousands
 9 Months Ended 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Mar. 31, 2016
Number of Shares (in shares)      
Beginning Balance (shares) 7,824,395    
Granted (shares) 1,525,500 3,336,650  
Forfeited / Cancelled (shares) (1,853,025)    
Exercised (shares) (18,038)    
Ending Balance (shares) 7,478,832   7,824,395
Vested and expected to vest (net of estimated forfeitures) (shares) 6,007,522    
Exercisable (shares) 3,275,088    
Weighted Average Exercise Price ($ per share)      
Options outstanding ($ per share) $ 3.61    
Granted ($ per share) 1.02    
Forfeited/Cancelled ($ per share) 3.02    
Exercised ($ per share) 0.64    
Options outstanding ($ per share) 3.22   $ 3.61
Vested and expected to vest (net of estimated forfeitures) ($ per share) 3.56    
Exercisable ($ per share) $ 4.97    
Weighted Average Remaining Contractual Life (in years)      
Outstanding 7 years 7 months 13 days   8 years 2 months 27 days
Vested and expected to vest (net of estimated forfeitures) 7 years 5 months 23 days    
Exercisable, December 31, 2016 5 years 11 months 27 days    
Aggregate Intrinsic Value (in $)      
Outstanding $ 21   $ 110
Vested and expected to vest (net of estimated forfeitures) 16    
Exercisable, December 31, 2016 $ 8