SUPPLEMENTAL CASH FLOW INFORMATION (Supplemental Information Referable to Condensed Consolidated Statements of Cash Flows) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SUPPLEMENTAL CASH FLOW INFORMATION [Abstract]
Interest (exclusive of amount capitalized)		$ 129,182	$ 129,224	$ 128,217
Income taxes		95,934	56,812	(65,968)
Accrued liabilities for purchases of property, plant & equipment		55,904	57,309	37,116
Recognition of new asset retirement obligations		353	263	20
Right-of-use assets obtained in exchange for new: Operating lease liabilities	[1]	49,586	444,547	0
Right-of-use assets obtained in exchange for new: Finance lease liabilities	[1]	6,631	1,227	0
Amounts referable to business acquisitions, Liabilities assumed		5,879	4,373	5,405
Amounts referable to business acquisitions, Consideration payable to seller		8,980	0	4,500
Amounts referable to business acquisitions, Fair value of noncash assets and liabilities exchanged		21,213	0	0
Debt issued for purchases of property, plant & equipment		$ 2,571	$ 0	$ 0

[1] The 2019 amount includes the initial right-of-use assets resulting from our adoption of ASU 2016-02, “Leases.”