BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Warranty, Accrued Liabilities, and Basic and Diluted Income per Share (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
Changes in the reserve for product warranty claims
Warranty reserve at beginning of the year	$ 1,075	$ 971	$ 922
Warranty reserves acquired	465		117
Provision	34	210	(13)
Warranty expenditures	(97)	(101)	(34)
Effect of foreign currency translation	94	(5)	(21)
Warranty reserve at end of year	1,571	1,075	971
ACCRUED LIABILITIES
Compensation and fringe benefits				$ 11,184	$ 12,967
Warranty reserve	$ 1,075	$ 1,075	$ 971	1,571	1,075
Income taxes payable				1,459	2,231
Right of use liabilities				4,666	3,203
Other accrued expenses				$ 5,982	$ 3,525
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]				Accrued liabilities	Accrued liabilities
Accrued liabilities				$ 24,862	$ 23,001
Basic and Diluted Income per Share
Basic weighted average shares outstanding	9,495	9,398	9,265
Dilutive effect of equity awards	60	63	105
Diluted weighted average shares outstanding	9,555	9,461	9,370
Minimum
Warranty
Warranty period	3 months
Maximum
Warranty
Warranty period	2 years