Net Loss Per Share - Antidilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of of diluted weighted average shares outstanding	17,249,162	17,642,935
Convertible preferred stock (as converted to common stock)
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of of diluted weighted average shares outstanding
Warrants to purchase convertible preferred stock (as converted to common stock)
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of of diluted weighted average shares outstanding
Unvested restricted common stock
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of of diluted weighted average shares outstanding	299,700	1,816,047
Stock options to purchase common stock
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of of diluted weighted average shares outstanding	16,949,462	15,826,888