Net Loss Per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net loss	$ (43,880)	$ (35,474)	$ (81,534)	$ (78,234)
Denominator:
Weighted-average number of common shares used in loss per share - basic and diluted (in shares)	46,420,046	46,109,193	46,345,585	45,891,557
Loss per share - basic and diluted (in dollars per share)	$ (0.95)	$ (0.77)	$ (1.76)	$ (1.70)