COMMITMENTS AND CONTINGENCIES (Narrative) (Details) $ in Thousands				1 Months Ended						12 Months Ended
	Dec. 30, 2020	Nov. 09, 2020 USD ($)	Nov. 08, 2020 USD ($)	Nov. 30, 2020 USD ($)	Oct. 31, 2018 mi	Dec. 31, 2017	Sep. 30, 2017 item	Mar. 31, 2016 mi	May 31, 2007 entity mi	Dec. 31, 2020 USD ($) item	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Expenditures under the noncapital purchase commitments										$ 87,438	$ 87,044	$ 56,674
Commitments of minimum royalties under mineral leases										265,560
Expenditures for mineral royalties under mineral leases										81,549	84,782	76,761
Asset retirement obligations										283,163	210,323	$ 225,726
Number of other companies to perform a Remedial Investigation/ Feasibility Study related to the Lower Passaic River Clean-Up lawsuit | entity									70
Number of miles of the River used in the Remedial Investigation/Feasibility Study | mi									17
Judge ruled allocation of fault among defendants, percentage	15.00%
Net liabilities										74,135	65,259
Lease liabilities										442,737	$ 419,176
Parent Company [Member]
Loss Contingencies [Line Items]
Judge ruled allocation of fault among defendants, percentage						15.00%
Property, Plant and Equipment [Member]
Loss Contingencies [Line Items]
Unconditional purchase obligations										6,947
Recorded unconditional purchase obligation in 2018										6,947
Noncapital [Member]
Loss Contingencies [Line Items]
Unconditional purchase obligations										46,165
Recorded unconditional purchase obligation in 2018										$ 16,005
New York Water District Cases [Member]
Loss Contingencies [Line Items]
Number of cases | item										27
NAFTA Arbitration [Member]
Loss Contingencies [Line Items]
Contingency loss										$ 0
EPA Administrative Order [Member]
Loss Contingencies [Line Items]
Amount of damages paid				$ 68
Cooperating Parties Group [Member]
Loss Contingencies [Line Items]
Number of miles for bank-to-bank dredging remedy | mi					9			8
Texas Brine and Occidental Chemical Co [Member]
Loss Contingencies [Line Items]
Judge ruled allocation of fault among defendants, percentage	20.00%
Occidental Chemical Co [Member]
Loss Contingencies [Line Items]
Judge ruled allocation of fault among defendants, percentage	30.00%					50.00%
Texas Brine [Member]
Loss Contingencies [Line Items]
Judge ruled allocation of fault among defendants, percentage	55.00%					35.00%
Number of cases | item										2
LADWP [Member]
Loss Contingencies [Line Items]
Number of planned new treatment capabilities | item										2
Minimum [Member] | NAFTA Arbitration [Member]
Loss Contingencies [Line Items]
Arbitration period										2 years
Maximum [Member] | EPA Administrative Order [Member]
Loss Contingencies [Line Items]
Total amount of damages claimed threshold		$ 300	$ 100
Maximum [Member] | EPA [Member]
Loss Contingencies [Line Items]
Estimated implementation costs										$ 1,380,000
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Outstanding standby letters of credit										56,080
Hewitt Landfill Matter [Member]
Loss Contingencies [Line Items]
Number of groundwater extraction wells | item							2
Surety Bond [Member]
Loss Contingencies [Line Items]
Contingency liability										$ 835,819
Number of surety bonds | item										522
Top Five Bonds [Member]
Loss Contingencies [Line Items]
Contingency liability										$ 206,015
Percentage of bonds										25.00%