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
Earnings Per Share [Abstract]
Net loss	$ (6,622)	$ (8,060)	$ (15,677)	$ (14,855)
Weighted average common shares outstanding (in shares)	101,150	93,745	100,862	90,283
Net loss per share, basic and diluted (in dollars per share)	$ (0.07)	$ (0.09)	$ (0.16)	$ (0.16)