Net Income (Loss) per Share - Anti-dilutive Securities (Details)	9 Months Ended
	Sep. 30, 2018 shares
Securities excluded from the calculation of diluted net loss per share attributable to common stockholders
Amount of antidilutive securities excluded from computation of earnings per share	3,773,215
Employee stock options
Securities excluded from the calculation of diluted net loss per share attributable to common stockholders
Amount of antidilutive securities excluded from computation of earnings per share	2,566,855
Restricted stock
Securities excluded from the calculation of diluted net loss per share attributable to common stockholders
Amount of antidilutive securities excluded from computation of earnings per share	1,063,681
Contingently issuable shares
Securities excluded from the calculation of diluted net loss per share attributable to common stockholders
Amount of antidilutive securities excluded from computation of earnings per share	142,679