Net Loss Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net loss	$ (18,478)	$ (12,463)	$ (36,255)	$ (27,180)
Denominator:
Weighted-average shares outstanding - basic and diluted	131,099	101,623	128,943	101,419
Net loss per common share - basic and diluted:	$ (0.14)	$ (0.12)	$ (0.28)	$ (0.27)