INCOME TAXES (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income before income tax expense
U.S. operations	$ 67,240	$ 62,609	$ 107,803
Foreign operations	30,911	15,983	19,735
Income before income tax expense	98,151	78,592	127,538
Current:
Federal	4,276	11,712	11,980
State	2,101	2,404	2,840
Foreign	13,673	3,918	4,588
Total current	20,050	18,034	19,408
Deferred:
Federal	6,297	(20,595)	23,814
State	908	2,541	2,347
Foreign	(2,359)	(1,580)	(145)
Total deferred	4,846	(19,634)	26,016
Income tax expense (benefit)	24,896	(1,600)	$ 45,424
Deferred tax assets
Accounts receivable, principally due to allowance for doubtful accounts	(32)	858
Inventories	5,939	5,939
Net operating loss carryforwards	6,898	7,460
Accrued pension	2,121	5,591
Stock-based compensation	3,722	2,972
Compensation-related accruals	696	3,063
Warranty	2,055	1,779
Obligation for post-employment benefits other than pension	935	1,312
Accrued liabilities and other items	8,350	3,886
Gross deferred tax assets	30,684	32,860
Valuation allowance	(4,789)	(4,789)
Net deferred tax assets	25,895	28,071
Deferred tax liabilities:
Intangibles	(85,553)	(58,701)
Plant and equipment	(26,839)	(24,041)
Gross deferred tax liabilities	(112,392)	(82,742)
Net deferred tax liabilities	$ (86,497)	$ (54,671)