Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (68,718)	$ (18,293)	$ (70,792)	$ (62,691)
Other comprehensive (loss) income:
Unrealized loss on available-for-sale securities, net of income tax benefit of $2,068 and $2,068, for the three and nine months ended September 30, 2017	0	5,047	0	3,903
Cumulative effect of ASU 2016-01 adoption on January 1, 2018 for unrealized gains on equity securities, net of income tax; recorded as a reclassification to “accumulated deficit” (see Note 3(a))	0	0	(17,211)	0
Foreign currency translation adjustments	(254)	405	(2,130)	1,349
Other comprehensive (loss) income	(254)	5,452	(19,341)	5,252
Total comprehensive loss	$ (68,972)	$ (12,841)	$ (90,133)	$ (57,439)