CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net income	$ 54,988	$ 31,966	$ 34,206
Other comprehensive loss:
Change in unrecognized pension and post-retirement benefit costs	(80)	(178)	(1,820)
Tax benefit on change in unrecognized pension and post-retirement benefit costs	29	36	699
Foreign currency translation adjustments	(2,420)	(13,848)	(7,670)
Tax (expense) benefit on foreign currency translation adjustments	(5,527)	3,341	770
Other comprehensive loss	(7,998)	(10,649)	(8,021)
Comprehensive loss attributable to non-controlling interest	(137)	(1,603)	(565)
Comprehensive income attributable to controlling interest	$ 47,127	$ 22,920	$ 26,750