CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income (loss)	$ 29,176	$ 36,054	$ 40,430	$ (163,513)
Other comprehensive income (loss):
Foreign currency translation	(38)	(3)	97	(46)
Unrealized gain (loss) on marketable securities, net of tax	214	(47)	(189)	(179)
Unrealized gain on long term investment, net of tax (Note 2)		1,548		15,484
Defined benefit pension obligations, net of tax	111	46	333	139
Other comprehensive income	287	1,544	241	15,398
Comprehensive income (loss)	$ 29,463	$ 37,598	$ 40,671	$ (148,115)