Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (37,763)	$ (29,037)	$ (72,965)	$ (59,217)
Other comprehensive income (loss):
Change in unrealized gains on marketable securities	353	0	723	0
Comprehensive loss	$ (37,410)	$ (29,037)	$ (72,242)	$ (59,217)