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
Earnings Per Share [Abstract]
Net loss	$ (6,251)	$ (9,519)	$ (21,928)	$ (24,374)
Weighted average common shares outstanding (in shares)	102,765	98,665	101,503	93,108
Net loss per share, basic and diluted (in dollars per share)	$ (0.06)	$ (0.10)	$ (0.22)	$ (0.26)