CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income (loss)	$ 52,394	$ (12,484)	$ 11,254	$ (199,567)
Other comprehensive income (loss):
Foreign currency translation	100	(36)	135	(43)
Unrealized gain (loss) on marketable securities, net of tax	102	(97)	(403)	(131)
Unrealized gain on long term investment, net of tax (Note 2)		5,677		13,935
Defined benefit pension obligations, net of tax	111	47	222	93
Other comprehensive income (loss)	313	5,591	(46)	13,854
Comprehensive income (loss)	$ 52,707	$ (6,893)	$ 11,208	$ (185,713)