INCOME TAXES - Tax Effects and Tax Cuts and Jobs Act (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of components of income before income taxes
Domestic		$ 8,076	$ 4,288	$ 7,676
Foreign		8,060	8,515	7,745
Income before income taxes		16,136	12,803	15,421
Current provision (benefit)
Domestic		4,750	(70)	1,936
Foreign		2,566	2,025	1,042
Total current provision		7,316	1,955	2,978
Deferred provision
Domestic		925	1,438	1,217
Foreign		(141)	332	152
Total deferred provision		784	1,770	1,369
Provision for income taxes		$ 8,100	$ 3,725	$ 4,347
Differences in the provision for income taxes from the amount determined by applying the federal statutory rate
Tax provision, computed at statutory rate (as a percent)		35.00%	34.00%	34.00%
State tax, net of federal impact (as a percent)		3.60%	4.60%	4.80%
Change in valuation allowance (as a percent)		1.90%	0.90%	(3.30%)
Effect of foreign tax rate differences (as a percent)		(4.20%)	(6.50%)	(6.10%)
Permanent items, other (as a percent)		0.20%	(0.40%)	0.90%
R&D Credit (as a percent)		(2.20%)	(1.70%)	(1.30%)
Restricted Stock Awards (as a percent)		(2.60%)	(2.70%)	0.00%
Effect of Tax Cuts and Job Act (as a percent)		19.40%	0.00%	0.00%
Other (as a percent)		(0.90%)	0.90%	(0.80%)
Provision for income taxes (as a percent)		50.20%	29.10%	28.20%
Effective tax rate excluding adjustments related to Tax Cuts and Jobs Act, Provision for income taxes
As reported		$ 8,100	$ 3,725	$ 4,347
Less: repatriation transition tax		(3,140)
Plus: remeasurement of deferred tax assets and liabilities		7
As adjusted		$ 4,967
Effective tax rate excluding adjustments related to Tax Cuts and Jobs Act, Tax rate
As reported (as a percent)		50.20%	29.10%	28.20%
Less: repatriation transition tax (as a percent)		(19.50%)
Plus: remeasurement of deferred tax assets and liabilities (as a percent)		0.10%
As adjusted (as a percent)		30.80%
Recognized provisional amount included as a component of income tax expense from continuing operations		$ 3,133
Noncurrent deferred tax assets:
Employee benefit plans		1,896	$ 2,247
Allowances and other		640	969
Net operating loss and tax credit carryforwards		203	1,003
Other		370	852
Total noncurrent deferred tax assets		3,109	5,071
Valuation allowance		(50)	(557)
Net noncurrent deferred tax assets:		3,059	4,514
Net noncurrent deferred tax liabilities:
Property and Equipment		3,001	3,445
Goodwill and Intangibles		3,398	3,136
Other		255	276
Total deferred tax liabilities		6,654	6,857
Net deferred tax asset/(deferred tax liability)		$ (3,595)	$ (2,343)
Forecast
Differences in the provision for income taxes from the amount determined by applying the federal statutory rate
Tax provision, computed at statutory rate (as a percent)	21.00%