CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) [Abstract]
Net income (loss)	$ (60,744)	$ 37,590	$ 54,988
Other comprehensive income (loss):
Change in unrecognized pension and post-retirement benefit costs	(162)	689	(80)
Tax (expense) benefit on change in unrecognized pension and post-retirement benefit costs	38	(69)	29
Foreign currency translation adjustments	(9,516)	6,699	(2,420)
Tax expense on foreign currency translation adjustments	0	0	(5,527)
Other comprehensive income (loss)	(9,640)	7,319	(7,998)
Comprehensive loss attributable to non-controlling interest	439	232	137
Comprehensive income (loss) attributable to controlling interest	$ (69,945)	$ 45,141	$ 47,127