COMMITMENTS AND CONTINGENCIES (Narrative) (Details) $ in Thousands	1 Months Ended					3 Months Ended		6 Months Ended	12 Months Ended
	Oct. 31, 2018 mi	Dec. 31, 2017 USD ($)	Sep. 30, 2017 item	Mar. 31, 2016 mi	May 31, 2007 entity mi	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Mar. 31, 2019 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Asset retirement obligations		$ 218,117				$ 225,726		$ 223,497	$ 225,726	$ 225,186	$ 215,421	$ 214,709
Number of groundwater extraction wells | item			2
Contingency loss								0
Operating lease liabilities								$ 428,309
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								25
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
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Outstanding standby letters of credit								54,530
Hewitt Landfill Matter [Member]
Loss Contingencies [Line Items]
Life-to-date total accruals								$ 34,271
Increase in accrual of liability for claims and litigation						$ 10,392	$ 8,640		$ 19,032