Net Loss per Share - Calculation of Basic and Diluted Net Loss 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
Earnings Per Share [Abstract]
Net loss	$ (272,035)	$ (151,726)	$ (654,362)	$ (360,235)
Weighted average common shares used for basic and diluted net loss per share computation (in shares)	92,540	89,792	91,820	89,144
Net loss per common share:
Basic and Diluted (in usd per share)	$ (2.94)	$ (1.69)	$ (7.13)	$ (4.04)