PROPERTY, PLANT AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment, total cost	$ 354,452		$ 292,537
Less: accumulated depreciation	(250,804)		(203,457)
Total net book value	103,648	[1]	89,080	[1]	$ 87,943
Assets held under capital leases (included in the above)
Assets held under capital leases (included in the above)	14,193		6,338
Less: accumulated depreciation	(5,151)		(2,579)
Total net book value	9,042		3,759
Depreciation of property, plant and equipment	26,991		23,106		$ 21,327
Land and buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, total cost	86,480		72,820
Machinery, fixtures and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, total cost	195,682		160,097
Assets held under capital leases (included in the above)
Assets held under capital leases (included in the above)	14,193		6,338
Other equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, total cost	16,121		13,682
Software licenses [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, total cost	53,143		40,627
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, total cost	$ 3,026		$ 5,311

[1] Reflects property, plant and equipment, net.