PROPERTY, PLANT & EQUIPMENT (Property, Plant and Equipment) (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Total, gross		$ 7,185,818	$ 6,891,287
Less allowances for depreciation, depletion and amortization		3,924,380	3,734,997
Total, net		3,261,438	3,156,290
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Total, gross	[1]	2,374,051	2,305,801
Buildings [Member]
Property, Plant and Equipment [Line Items]
Total, gross		127,369	124,950
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total, gross		4,316,243	4,124,808
Leaseholds [Member]
Property, Plant and Equipment [Line Items]
Total, gross		17,595	14,143
Deferred Asset Retirement Costs [Member]
Property, Plant and Equipment [Line Items]
Total, gross		168,258	166,252
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total, gross		182,302	155,333
Depletable Land [Member]
Property, Plant and Equipment [Line Items]
Total, gross		$ 1,327,402	$ 1,296,211

[1] Includes depletable land, as follows: December 31, 2016 - $1,327,402 thousand and December 31, 2015 - $1,296,211 thousand.