Net Loss Per Share - Antidilutive Potential Common Shares (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive potential common shares	36,135,627	30,697,595
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive potential common shares	4,578,520	2,102,124
Convertible preferred stock (as converted to common stock)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive potential common shares	31,557,107	28,595,471