SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period		$ 1,781	$ 1,747	$ 1,989
Charged to costs and expenses		139	(163)	295
Charged to other accounts	[1]	(132)	281	303
Deductions	[2]	(43)	(84)	(840)
Balance at end of period		1,745	1,781	1,747
Allowance for Excess and Obsolete Inventory [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period		6,263	5,268	6,809
Charged to costs and expenses		3,893	3,513	2,186
Charged to other accounts	[1]	661	185	(59)
Deductions	[2]	(2,521)	(2,703)	(3,668)
Balance at end of period		8,296	6,263	5,268
Deferred Tax Assets - Valuation Allowances [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period		7,485	6,635	6,692
Charged to costs and expenses		1,599	887	456
Charged to other accounts	[1]	0	0	0
Deductions	[2]	(739)	(37)	(513)
Balance at end of period		$ 8,345	$ 7,485	$ 6,635

[1] Includes foreign currency translation adjustments

[2] Write offs