Quarterly report pursuant to Section 13 or 15(d)

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

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Description of Stock Plans - Summary of Options Granted Under All Equity Plans (Details) - Stock Option - USD ($)
$ / shares in Units, $ in Thousands
 9 Months Ended 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Mar. 31, 2017
Number of Shares (in shares)      
Beginning Balance (shares) 9,735,778    
Granted (shares) 1,338,778 1,525,500  
Forfeited / Cancelled (shares) (972,299)    
Exercised (shares) (182,769)    
Ending Balance (shares) 9,919,488   9,735,778
Vested and expected to vest (net of estimated forfeitures) (shares) 8,984,997    
Exercisable (shares) 5,065,645    
Weighted Average Exercise Price ($ per share)      
Options outstanding (in dollars per share) $ 2.56    
Granted (in dollars per share) 1.17    
Forfeited/Cancelled (in dollars per share) 1.91    
Exercised (in dollars per share) 1.05    
Options outstanding (in dollars per share) 2.48   $ 2.56
Vested and expected to vest (net of estimated forfeitures) (in dollars per share) 2.63    
Exercisable (in dollars per share) $ 3.81    
Weighted Average Remaining Contractual Life (in years)      
Outstanding 7 years 4 months 10 days   7 years 11 months 12 days
Vested and expected to vest (net of estimated forfeitures) 7 years 2 months 10 days    
Exercisable, December 31, 2017 5 years 11 months 20 days    
Aggregate Intrinsic Value (in thousands)      
Outstanding $ 4,977   $ 801
Vested and expected to vest (net of estimated forfeitures) 4,228    
Exercisable, December 31, 2017 $ 1,196