Net Loss Per Share - Antidilutive Securities Excluded from Computation of Net Loss per Share (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Securities excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from calculation of diluted net loss per share	8,667,265	6,203,885
Options to purchase common shares
Securities excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from calculation of diluted net loss per share	8,560,514	5,982,134
Warrants to purchase common shares
Securities excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from calculation of diluted net loss per share	106,751	221,751