PROPERTY, PLANT & EQUIPMENT (Property, Plant and Equipment) (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total, gross		$ 8,457,619	$ 7,969,312
Less allowances for depreciation, depletion and amortization		4,220,312	4,050,381
Total, net		4,237,307	3,918,931
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Total, gross	[1]	2,823,092	2,742,285
Buildings [Member]
Property, Plant and Equipment [Line Items]
Total, gross		139,948	135,655
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total, gross		5,106,918	4,740,212
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total, gross		18,217	17,354
Deferred Asset Retirement Costs [Member]
Property, Plant and Equipment [Line Items]
Total, gross		183,324	172,631
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total, gross		186,120	161,175
Depletable Land [Member]
Property, Plant and Equipment [Line Items]
Total, gross		$ 1,626,899	$ 1,606,303

[1] Includes depletable land, as follows: December 31, 2018 - $1,626,899 thousand and December 31, 2017 - $1,606,303 thousand.