CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT (Parenthetical) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Issuance cost $ 3,548    
Series A redeemable convertible preferred stock      
Net of issuance cost     $ 13
Series B convertible preferred stock      
Net of issuance cost   $ 433  
Series C convertible preferred stock      
Net of issuance cost $ 214