Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net loss	$ (7,652)	$ (24,060)	$ (14,365)	$ (6,251)	$ (6,622)	$ (9,055)	$ (46,077)	$ (21,928)
Weighted average common shares outstanding (in shares)	106,239			102,765			105,510	101,503
Net loss per share, basic and diluted (in dollars per share)	$ (0.07)			$ (0.06)			$ (0.44)	$ (0.22)