Net Loss Per Share - Summary of Calculation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net loss allocable to common stockholders	$ (9,527)	$ (46,235)	$ (15,635)	$ (70,450)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stockholders—basic and diluted	106,884	5,260	103,035	4,999
Net loss per share, basic and diluted	$ (0.09)	$ (8.79)	$ (0.15)	$ (14.09)