CHANGES IN ACCUMULATED OTHER COMPREHENSIVE LOSS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in AOCI by component
Beginning balance, net of tax	$ (54,656)	$ (48,713)	$ (38,801)
Other comprehensive (loss) income before reclassifications	14,621	(9,342)	(13,417)
Total before tax	(2,303)	(3,770)	(2,874)
Net other comprehensive (loss) income	16,924	(5,572)	(10,543)
Income taxes	494	371	(631)
Ending balance, net of tax	(38,226)	(54,656)	(48,713)
Foreign currency translation adjustment:
Changes in AOCI by component
Beginning balance, net of tax	15,483	20,529	25,913
Other comprehensive (loss) income before reclassifications	10,493	(4,811)	(4,598)
Total before tax	833	0	0
Net other comprehensive (loss) income	9,660	(4,811)	(4,598)
Income taxes	(206)	235	786
Ending balance, net of tax	25,349	15,483	20,529
Retirement plans related adjustments
Changes in AOCI by component
Beginning balance, net of tax	(70,102)	(69,100)	(64,570)
Other comprehensive (loss) income before reclassifications	4,173	(4,594)	(8,607)
Total before tax	(3,547)	(3,695)	(2,662)
Net other comprehensive (loss) income	7,720	(899)	(5,945)
Income taxes	821	103	(1,415)
Ending balance, net of tax	(63,203)	(70,102)	(69,100)
Unrealized gain (loss) on cash flow hedges
Changes in AOCI by component
Beginning balance, net of tax	(37)	(142)	(144)
Other comprehensive (loss) income before reclassifications	(45)	63	(212)
Total before tax	411	(75)	(212)
Net other comprehensive (loss) income	(456)	138	0
Income taxes	(121)	33	(2)
Ending balance, net of tax	$ (372)	$ (37)	$ (142)