Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net loss available for common shareholders - basic and diluted	$ (8,459)	$ (5,656)	$ (15,591)	$ (11,605)
Denominator:
Weighted-average shares outstanding - basic and diluted	81,321	69,373	79,973	68,747
Net loss per share - basic and diluted	$ (0.10)	$ (0.08)	$ 0.19	$ (0.17)