QUARTERLY FINANCIAL INFORMATION (UNAUDITED) - Summary of the unaudited quarterly financial information (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
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 Income	11,329	12,026	11,601	8,838	9,582	7,070	8,537	6,351
Net Income	$ 10,799	$ 8,677	$ 7,600	$ 6,670	$ 9,296	$ 4,456	$ 5,425	$ 3,839	$ 33,746	$ 23,016	$ 19,922
Basic Income Per Share (in dollars per share)	$ 0.95	$ 0.76	$ 0.67	$ 0.59	$ 0.81	$ 0.39	$ 0.48	$ 0.34	$ 2.96	$ 2.02	$ 1.76
Diluted Income Per Share (in dollars per share)	0.95	0.76	0.67	0.59	0.81	0.39	0.48	0.34	2.96	2.02	1.75
Cash Dividends Declared Per Share (in dollars per share)	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.72	$ 0.72	$ 0.68