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		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss		$ (209,383)	$ (419,503)	$ (123,914)
Denominator:
Shares used in per share calculation (in shares)		53,706	43,078	37,884
Net loss per share, basic and diluted (in dollars per share)	[1]	$ (3.90)	$ (9.74)	$ (3.27)

[1] Net loss per share for both continuing operations and discontinued operations, basic and diluted, was the same for all periods presented.