BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Warranty, Accrued Liabilities, and Basic and Diluted Income per Share (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Changes in the reserve for product warranty claims
Warranty reserve at beginning of the year	$ 830	$ 780	$ 786
Warranty reserves acquired		297
Provision	234	(138)	142
Warranty expenditures	(200)	(96)	(123)
Effect of foreign currency translation	58	(13)	(25)
Warranty reserve at end of year	922	830	780
Accrued Liabilities
Compensation and fringe benefits				$ 7,459	$ 7,379
Warranty reserve	$ 830	$ 780	$ 786	922	830
Income taxes payable				2,397	183
Other accrued expenses				3,492	2,286
Accrued liabilities				$ 14,270	$ 10,678
Basic and Diluted Income per Share from Continuing Operations
Dilutive effect of outstanding stock option awards (in shares)	105,000	94,000	10,000
Stock awards excluded from the calculation of diluted income per share (in shares)	600	30,700	0
Minimum
Warranty
Warranty period	3 months
Maximum
Warranty
Warranty period	2 years