COMMITMENTS AND CONTINGENCIES (Narrative) (Details)	1 Months Ended			3 Months Ended	12 Months Ended			24 Months Ended
	Jun. 30, 2019 USD ($)	Dec. 31, 2017 USD ($)	May 31, 2007 entity mi	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Expenditures under the noncapital purchase commitments					$ 87,044,000	$ 56,674,000	$ 40,526,000
Commitments of minimum royalties under mineral leases				$ 266,345,000	266,345,000			$ 266,345,000
Expenditures for mineral royalties under mineral leases					84,782,000	76,761,000	67,933,000
Asset retirement obligations		$ 218,117,000		210,323,000	210,323,000	225,726,000	218,117,000	210,323,000
Unrecognized tax benefits		$ 11,643,000		5,442,000	5,442,000	3,661,000	$ 11,643,000	5,442,000	$ 10,828,000
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
Increase in accrual of liability for claims and litigation								37,304,000
Operating lease liabilities				418,013,000	418,013,000			418,013,000
Net liabilities				65,259,000	65,259,000	$ 61,952,000		65,259,000
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				27,724,000	27,724,000			27,724,000
Noncapital [Member]
Loss Contingencies [Line Items]
Unconditional purchase obligations				48,516,000	$ 48,516,000			48,516,000
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]
Total amount of damages claimed	$ 193,750
Occidental Chemical Co [Member]
Loss Contingencies [Line Items]
Judge ruled allocation of fault among defendants, percentage		50.00%
Texas Brine [Member]
Loss Contingencies [Line Items]
Judge ruled allocation of fault among defendants, percentage		35.00%
Number of cases | item					2
Minimum [Member] | NAFTA Arbitration [Member]
Loss Contingencies [Line Items]
Arbitration period					2 years
Maximum [Member] | EPA [Member]
Loss Contingencies [Line Items]
Estimated implementation costs					$ 1,380,000,000
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Outstanding standby letters of credit				52,600,000	52,600,000			52,600,000
Hewitt Landfill Matter [Member]
Loss Contingencies [Line Items]
Increase in accrual of liability for claims and litigation				3,033,000
Surety Bond [Member]
Loss Contingencies [Line Items]
Contingency liability				686,627,000	$ 686,627,000			686,627,000
Number of surety bonds | item					441
Top Five Bonds [Member]
Loss Contingencies [Line Items]
Contingency liability				$ 168,020,000	$ 168,020,000			$ 168,020,000
Percentage of bonds					24.00%