Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Numerator [Abstract]
Net loss	$ (13,944)	$ (15,038)	$ (36,493)	$ 4,099	$ (10,040)	$ 8,451	$ (5,897)	$ (1,457)	$ (61,376)	$ (8,943)
Denominator [Abstract]
Weighted-average number of common shares - basic and diluted (in shares)									20,725,526
Loss per common share - basic and diluted (in dollars per share)	$ (0.56)	$ (0.64)	$ (1.90)	$ 0.27					$ (2.96)
Stock Options [Member]
Dilutive Instruments [Abstract]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding (in shares)									1,033,492
Unvested Restricted Stock Units [Member]
Dilutive Instruments [Abstract]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding (in shares)									205,175