Net Loss Per Share - Antidilutive Shares (Details) - shares
6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Total (in shares) 55,700,895 44,941,675
Common and preferred stock warrants    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Total (in shares) 7,623,436 4,865,722
Common stock options    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Total (in shares) 44,929,906 40,075,953
Restricted stock units    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Total (in shares) 3,147,553 0