Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) [Abstract]
Net income (loss)	$ 23,361	$ (40,768)	$ 37,579	$ (20,552)
Other comprehensive income (loss):
Foreign currency translation adjustments	(110)	(8,021)	853	(6,309)
Change in unrecognized pension benefit cost	0	0	0	65
Other comprehensive income (loss)	(110)	(8,021)	853	(6,244)
Comprehensive income (loss)	23,251	(48,789)	38,432	(26,796)
Comprehensive loss attributable to non-controlling interest	3	237	62	285
Comprehensive income (loss) attributable to controlling interest	$ 23,254	$ (48,552)	$ 38,494	$ (26,511)