COMMITMENTS AND CONTINGENCIES (Narrative) (Details)	1 Months Ended					3 Months Ended			12 Months Ended
	Oct. 31, 2018 mi	Dec. 31, 2017 USD ($)	Sep. 30, 2017 item	Mar. 31, 2016 mi	May 31, 2007 entity mi	Mar. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Asset retirement obligations		$ 218,117,000				$ 225,186,000	$ 225,726,000		$ 225,726,000	$ 214,709,000
Number of groundwater extraction wells | item			2
Contingency loss						0
Operating lease liabilities						$ 434,681,000
Parent Company [Member]
Loss Contingencies [Line Items]
Judge ruled allocation of fault among defendants, percentage		15.00%
New York Water District Cases [Member]
Loss Contingencies [Line Items]
Number of cases | item						14
Cooperating Parties Group [Member]
Loss Contingencies [Line Items]
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
Number of miles for bank-to-bank dredging remedy | mi	9			8
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						54,530,000
Hewitt Landfill Matter [Member]
Loss Contingencies [Line Items]
Life-to-date total accruals						$ 34,271,000
Increase in accrual of liability for claims and litigation							$ 10,392,000	$ 8,640,000	$ 19,032,000