SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 5) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Net Sales	$ 179,968	$ 195,690	$ 176,888	$ 159,160	$ 159,716	$ 153,363	$ 153,089	$ 148,933	$ 711,706	$ 615,101	$ 601,119
OPERATING EXPENSES:
Costs of Operations									628,370	548,000	536,840
Income Tax Provision									7,917	7,323	11,155
Net Income	$ 10,799	$ 8,677	$ 7,600	$ 6,670	$ 9,296	$ 4,456	$ 5,425	$ 3,839	33,746	$ 23,016	$ 19,922
ASU 2014-09 | Balances Without Adoption of ASU 2014-09
Revenues
Net Sales									711,672
OPERATING EXPENSES:
Costs of Operations									628,343
Income Tax Provision									7,916
Net Income									33,740
ASU 2014-09 | Effect of Adoption Increase/(Decrease)
Revenues
Net Sales									34
OPERATING EXPENSES:
Costs of Operations									27
Income Tax Provision									1
Net Income									$ 6