Net Loss Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net loss	$ (16,310)	$ (102,362)	$ (52,565)	$ (129,542)
Denominator:
Weighted-average shares outstanding - basic and diluted	133,417	103,096	130,434	101,984
Net loss per common share - basic and diluted:	$ (0.12)	$ (0.99)	$ (0.40)	$ (1.27)