CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income (loss)	$ 102,312	$ (41,140)
Other comprehensive income (loss)
Foreign currency translation	126	35
Unrealized gain (loss) on marketable securities, net of tax	681	(505)
Defined benefit pension obligations, net of tax	111	111
Other comprehensive income (loss)	918	(359)
Comprehensive income (loss)	$ 103,230	$ (41,499)