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ENVIRONMENTAL MATTERS AND ASSET RETIREMENT OBLIGATIONS (Details) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2021
Dec. 31, 2020
Accrual for Environmental Loss Contingencies [Roll Forward]    
Beginning of period $ 285  
End of period 282 $ 285
Accrual for Environmental Loss Contingencies, Balance Sheet Classification [Abstract]    
Accrued Environmental Loss Contingencies, Current 15 15
Accrued Environmental Loss Contingencies, Noncurrent 267 270
Environmental Remediation [Member]    
Accrual for Environmental Loss Contingencies [Roll Forward]    
Beginning of period 257 260
Changes in estimates recognized in earnings and other 1 7
Cash reductions (3) (10)
End of period $ 255 257
Expected Payment Period of Environmental Contingencies approximately 30 years  
Environmental Remediation [Member] | Minimum [Member]    
Site Contingency [Line Items]    
Loss Contingency, Estimate of Possible Loss $ 255 257
Environmental Remediation [Member] | Maximum [Member]    
Site Contingency [Line Items]    
Loss Contingency, Estimate of Possible Loss 497 501
Environmental ARO [Member]    
Site Contingency [Line Items]    
Best Estimate Accrued to-date For Asset Retirement Obligation 27 28
Non Environmental ARO [Member]    
Site Contingency [Line Items]    
Best Estimate Accrued to-date For Asset Retirement Obligation $ 51 $ 51