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ASSET RETIREMENT OBLIGATION - Schedule of changes to Asset Retirement Obligation (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Asset retirement obligation at beginning of year $ 1,932 $ 1,835
Liabilities incurred 41 51
Liabilities divested (56) 0
Liabilities settled (56) (52)
Accretion expense 107 108
Revisions in estimated liabilities (110) (10)
Asset retirement obligation at end of year 1,858 1,932
Less current portion (47) (66)
Asset retirement obligation, long-term $ 1,811 $ 1,866