Description of Business and Basis of Presentation (Net Income (Loss) per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator
Net loss	$ (9,205)	$ (10,399)
Denominator
Basic and diluted (in shares)	37,522	32,197
Net loss per share
Basic and diluted (in dollars per share)	$ (0.25)	$ (0.32)