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Stock Based Compensation (Details) - USD ($)
12 Months Ended
Aug. 12, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-Based Compensation        
Vesting period   4 years    
Fair value assumptions        
Stock-based compensation expense   $ 4,053,000 $ 1,653,000 $ 578,000
Employee Stock Purchase Plan        
Share-Based Compensation        
Shares available for grant   156,891    
Number of shares issued under the plan        
Shares available for authorized   220,588    
Fair value assumptions        
Percentage of full share price paid in purchase of common stock   85.00%    
Maximum amount of annual employee common stock purchases   $ 25,000    
Stock-based compensation expense   233,000 103,000  
Percentage of shares outstanding 1.00%      
2006 and 2014 Stock Option Plans | Options to purchase common shares        
Share-Based Compensation        
Aggregate fair value of options granted   $ 10,100,000 $ 6,000,000 $ 2.0
Number of Shares        
Outstanding, beginning of the period (in shares)   2,911,146    
Granted (in shares)   1,194,483    
Exercised (in shares)   (378,991)    
Cancelled (in shares)   (242,340)    
Outstanding, end of the period (in shares)   3,484,298 2,911,146  
Exercisable (in shares)   1,730,186    
Vested or expected to vest (in shares)   3,323,663    
Weighted Average Exercise Price Per Share        
Outstanding, beginning of the period (in dollars per share)   $ 5.30    
Granted (in dollars per share)   15.86    
Exercised (in dollars per share)   2.95    
Cancelled (in dollars per share   10.87    
Outstanding, end of the period (in dollars per share)   8.79 $ 5.30  
Exercisable (in dollars per share)   5.17    
Vested or expected to vest (in dollars per share)   $ 8.58    
Weighted-Average Remaining Contractual Term (in years)        
Outstanding (in years)   7 years 7 months 21 days 7 years 10 months 13 days  
Exercisable (in years)   6 years 4 months 2 days    
Vested or expected to vest (in years)   7 years 6 months 26 days    
Aggregate Intrinsic Value        
Outstanding, beginning of the period   $ 40,586,000    
Exercised (in dollars)   4,513,000    
Outstanding, end of the period   14,620,000 $ 40,586,000  
Exercisable   11,648,000    
Vested or expected to vest   $ 14,450,000    
Fair value assumptions        
Weighted average fair value of options granted (in dollars per share)   $ 8.42 $ 7.59 $ 1.85
Weighted-average risk-free interest rate   1.69% 1.91% 1.68%
Expected dividend yield   0.00% 0.00% 0.00%
Expected volatility   56.00% 61.00% 63.00%
Expected terms   6 years 5 years 10 months 24 days 6 years
Fair value of stock options vested   $ 4,000,000 $ 1,200,000 $ 476,000
2006 Stock Option Plan | Maximum | Options to purchase common shares        
Share-Based Compensation        
Expiration Period   10 years    
Vesting period   4 years    
2014 Stock Option Plan | Options to purchase common shares        
Share-Based Compensation        
Shares available for future issuance under stock incentive plan   823,529    
Percentage of common shares outstanding   4.00%    
Shares available for grant   395,133    
2014 Stock Option Plan | Maximum | Options to purchase common shares        
Share-Based Compensation        
Expiration Period   10 years    
Vesting period   4 years