CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (123,194)	$ (80,331)	$ (390,905)	$ (243,308)
Other comprehensive income (loss):
Unrealized gain on available-for-sale debt securities, net of tax, $25 and $0, for three months ended September 30, 2019 and 2018, respectively, and net of tax, $1,173 and $0, for nine months ended September 30, 2019 and 2018, respectively	168	458	4,243	197
Less: amounts recognized for net realized (gain)/loss included in net loss	(79)	629	(93)	38
Total other comprehensive income	89	1,087	4,150	235
Comprehensive loss	$ (123,105)	$ (79,244)	$ (386,755)	$ (243,073)