SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning of period	$ 68,764	$ 67,240	$ 67,158
Costs and expenses	3,012	5,747	5,841
Other accounts	1,367	963	314
Deductions	27,844	3,671	4,946
Currency translation adjustments	2,740	(1,515)	(1,127)
End of period	48,039	68,764	67,240
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning of period	796	873	1,062
Costs and expenses	512	215	135
Other accounts	(6)	41	0
Deductions	575	280	271
Currency translation adjustments	56	(53)	(53)
End of period	783	796	873
Inventory Valuation Reserve [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning of period	22,956	22,704	21,307
Costs and expenses	2,011	3,612	3,995
Other accounts	1,373	0	314
Deductions	8,140	2,829	2,521
Currency translation adjustments	1,019	(531)	(391)
End of period	19,219	22,956	22,704
Valuation Allowance of Deferred Tax Assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning of period	45,012	43,663	44,789
Costs and expenses	489	1,920	1,711
Other accounts	0	922	0
Deductions	19,129	562	2,154
Currency translation adjustments	1,665	(931)	(683)
End of period	$ 28,037	$ 45,012	$ 43,663