SEGMENT INFORMATION (Geographic Split of Net Sales and Property, Plant and Equipment ) (Details) - 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
Geographic split of the Company's net sales, based on the location of the customer, and property, plant and equipment
Net sales	$ 743,827	$ 737,099	$ 790,052	$ 757,696	$ 747,185	$ 669,491	$ 626,858	$ 580,897	$ 3,028,674	$ 2,624,431	$ 2,274,614
Total property, plant and equipment, net	$ 478,801				$ 477,031				$ 478,801	$ 477,031	$ 372,377
Percentage of LIFO Inventory	37.00%				32.00%				37.00%	32.00%	40.00%
United States
Geographic split of the Company's net sales, based on the location of the customer, and property, plant and equipment
Net sales									$ 1,554,688	$ 1,388,816	$ 1,308,635
Total property, plant and equipment, net	$ 214,943				$ 194,491				214,943	194,491	176,041
Other foreign countries
Geographic split of the Company's net sales, based on the location of the customer, and property, plant and equipment
Net sales									1,473,986	1,235,615	965,979
Total property, plant and equipment, net	264,110				282,931				264,110	282,931	196,679
Corporate / Eliminations
Geographic split of the Company's net sales, based on the location of the customer, and property, plant and equipment
Total property, plant and equipment, net	$ (252)				$ (391)				$ (252)	$ (391)	$ (343)
Customer Concentration Risk [Member] | Sales Revenue, Goods, Net [Member] | Maximum
Geographic split of the Company's net sales, based on the location of the customer, and property, plant and equipment
Concentration Risk, Percentage									10.00%	10.00%	10.00%