XML 56 R43.htm IDEA: XBRL DOCUMENT v3.10.0.1
Stock-based Compensation - Restricted Stock and Stock Options (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Dec. 31, 2014
Changes in unvested restricted stock            
Unvested restricted common stock, beginning of period (in shares)     513,225      
Vested (in shares)     (225,225)      
Unvested restricted common stock, end of period(in shares) 288,000   288,000   513,225  
Weighted Average Grant Date Fair Value            
Balance, beginning of period     $ 18.70      
Vested (in dollars per share)     6.75      
Balance, ending of period $ 28.05   $ 28.05   $ 18.70  
Changes in unvested stock options            
Compensation expense $ 6,699 $ 4,468 $ 20,251 $ 15,287    
Options exercised prior to vesting (in shares)           75,304
Options exercised prior to vesting , exercise price per share           $ 0.03
Outstanding, beginning of period (in shares)     4,372,136      
Granted (in shares)     1,643,185      
Exercised (in shares)     (634,331)      
Cancelled (in shares)     (558,504)      
Outstanding, end of period (in shares) 4,822,486   4,822,486   4,372,136  
Exercisable (in shares) 1,881,620   1,881,620      
Outstanding, beginning of period (in dollars per share)     $ 17.28      
Granted (in dollars per share)     36.29      
Exercised (in dollars per share)     13.73      
Cancelled (in dollars per share)     24.88      
Outstanding, end of period (in dollars per share) $ 23.38   23.38   $ 17.28  
Exercisable (in dollar per share) $ 17.65   $ 17.65      
Remaining contractual life     8 years 2 months 12 days   8 years 6 months  
Exercisable, remaining contractual life     7 years 6 months      
Aggregate intrinsic value $ 48,750   $ 48,750   $ 60,591  
Exercisable, aggregated intrinsic value $ 28,201   $ 28,201      
Unvested stock options (in shares) 0   0   4,572  
Employees and directors            
Changes in unvested stock options            
Compensation expense     $ 14,900 $ 9,100    
Unrecognized stock-based compensation expense $ 51,800   $ 51,800      
Weighted average fair value of options granted (per share)     $ 25.65 $ 16.71    
Restricted Stock | Employees            
Changes in unvested stock options            
Compensation expense     $ 0      
Unrecognized stock-based compensation expense 0   0      
Restricted Stock | Non-employees            
Changes in unvested stock options            
Compensation expense     1,900      
Unrecognized stock-based compensation expense $ 9,000   $ 9,000