Net Loss Per Share Attributable to Common Stockholders - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net loss attributable to common stockholders	$ (7,013)	$ (8,985)	$ (13,560)	$ (14,881)
Denominator:
Weighted-average common shares outstanding - basic and diluted	39,175	13,036	38,793	13,016
Net loss per common share - basic and diluted	$ (0.18)	$ (0.69)	$ (0.35)	$ (1.14)