Net Loss per Share - Antidilutive Securities Excluded from Computation of Net Loss per Share (Details) - shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Securities excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from calculation of diluted net loss per share	8,413,210	6,241,321
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	8,306,459	6,019,570
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