PROPERTY, PLANT & EQUIPMENT (Property, Plant and Equipment) (Details) - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total, gross		$ 9,102,086	$ 8,749,218
Less allowances for depreciation, depletion and amortization		4,676,087	4,433,180
Total, net		4,425,999	4,316,038
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Total, gross	[1]	3,013,327	2,920,963
Buildings [Member]
Property, Plant and Equipment [Line Items]
Total, gross		145,418	141,898
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total, gross		5,517,897	5,362,279
Finance Leases [Member]
Property, Plant and Equipment [Line Items]
Total, gross		7,796	1,677
Deferred Asset Retirement Costs [Member]
Property, Plant and Equipment [Line Items]
Total, gross		240,743	167,484
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total, gross		176,905	154,917
Depletable Land [Member]
Property, Plant and Equipment [Line Items]
Total, gross		$ 1,712,059	$ 1,667,642

[1] Includes depletable land as follows: December 31, 2020 — $1,712,059 thousand and December 31, 2019 — $1,667,642 thousand.