XML 52 R42.htm IDEA: XBRL DOCUMENT v3.19.2
Net loss per share (Details) - shares
6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share    
Antidilutive shares excluded from the calculation of diluted earnings per share, total 2,960,335 7,477,380
Options    
Antidilutive Securities Excluded from Computation of Earnings Per Share    
Antidilutive shares excluded from the calculation of diluted earnings per share, total 2,420,508  
Unvested restricted stock    
Antidilutive Securities Excluded from Computation of Earnings Per Share    
Antidilutive shares excluded from the calculation of diluted earnings per share, total 539,827 108,486
Redeemable convertible preferred stock (as converted to common stock)    
Antidilutive Securities Excluded from Computation of Earnings Per Share    
Antidilutive shares excluded from the calculation of diluted earnings per share, total   7,368,894