Net Loss Per Share - Reconciliation of Numerator and Denominators in Computing Net Loss per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net loss from continuing operations	$ (37,763)	$ (28,839)	$ (72,965)	$ (59,019)
Shares used in per share calculation (in shares)	42,458	35,355	42,348	35,099
Net loss from continuing operations per share, basic and diluted (in dollars per share)	$ (0.89)	$ (0.82)	$ (1.72)	$ (1.68)