Nature of Business and Basis of Presentation - Initial Public Offering - Conversion (Details) - shares
May 08, 2018
Mar. 31, 2018
Dec. 31, 2017
Initial Public Offering      
Common stock issued upon conversion of redeemable preferred stock (in shares) 46,079,623    
Common stock, shares outstanding (in shares) 67,339,488 11,412,802 11,139,690
Common stock warrants      
Initial Public Offering      
Common stock issued upon exercise of warrants (in shares) 485,985