Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Not Included in Calculation of Earnings per Share (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,677,878	28,205,275
Redeemable convertible preferred stock outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	21,233,190
Redeemable convertible preferred stock warrants outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	2,672,502
Common stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,677,878	4,292,056
Common stock warrants outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	7,527