Annual report pursuant to Section 13 and 15(d)

Stockholder's Equity - Shares Available for Future Issuance (Details)

v3.3.1.900
Stockholder's Equity - Shares Available for Future Issuance (Details) - USD ($)
$ / shares in Units, $ in Millions
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Weighted-average assumptions:          
Estimated annual forfeiture rate (as a percent) 9.00% 7.00%      
Shares Available for Future Grant          
Balance at the end of the period (in shares) 959,354        
Shares Reserved for Future Issuance          
Stock options outstanding (in shares)     4,630,073    
Shares available for future grant under 2013 Plan (in shares) 959,354   959,354    
Employee stock purchase plan     225,806    
Warrants outstanding (in shares)     62,800    
Total shares of common stock reserved for issuance     5,878,033    
2013 plan          
Shares Available for Future Grant          
Balance at the beginning of the period (in shares) 829,364        
Authorized (in shares)     1,569,646    
Granted (in shares) (1,645,960)        
Forfeitures/Expirations (in shares) 206,304        
Balance at the end of the period (in shares) 959,354 829,364      
Shares Reserved for Future Issuance          
Shares available for future grant under 2013 Plan (in shares) 829,364 829,364 959,354 829,364  
Options outstanding          
Equity Incentive Plans          
Intrinsic value of options exercisable     $ 14.4    
Per share price of Company's closing stock price (in dollars per share)     $ 10.50    
Weighted average exercise price (in dollars per share)     $ 3.10    
Per-share weighted-average grant date fair value of options granted (in dollars per share) $ 4.49 $ 4.43      
Weighted-average assumptions:          
Unrecognized compensation expense     $ 9.0    
Weighted average remaining period for recognition of unrecognized compensation expense 2 years 9 months 4 days        
Shares Reserved for Future Issuance          
Stock options outstanding (in shares)     4,630,073 3,574,450 2,795,746
Options outstanding | Weighted-average          
Weighted-average assumptions:          
Expected term of options (in years) 6 years 2 months 12 days 5 years 9 months 18 days      
Risk-free interest rate (as a percent) 1.70% 1.80%      
Expected volatility (as a percent) 68.50% 75.90%      
Dividend yield (as a percent) 0.00% 0.00%