Net Loss Per Share - Computation of Basic and Diluted Loss Per Share Attributable to Common Stockholders (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	$ (24,956)	$ (25,467)	$ (47,329)	$ (51,611)
Denominator:
Weighted average common shares outstanding - basic and diluted	89,080,046	62,651,863	88,980,353	62,599,371
Net loss per share - basic and diluted	$ (0.28)	$ (0.41)	$ (0.53)	$ (0.82)