INVENTORIES (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
INVENTORIES [Abstract]
Inventory classified as long-term assets (other noncurrent assets)	$ 10,978	$ 7,557
Inventories valued under the LIFO method	307,656	309,429
Increase (decrease) in cost of revenues due to the effect of the LIFO liquidation	(867)	(1,147)	$ 132
Increase (decrease) in net earnings due to the effect of the LIFO liquidation	646	854	(99)
Excess of estimated current cost over LIFO cost	192,974	183,181
Approximate effect on net earnings due to the adoption of the LIFO method	$ 7,292	$ 5,462	$ 5,223