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ASSET RETIREMENT OBLIGATIONS Asset Retirement Obligations - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Available-for-sale Securities $ 31 $ 26  
Asset Retirement Obligation, Revision of Estimate 9 (33) $ 1
Asset Retirement Obligation, Liabilities Settled 2 1 $ 1
Other ARO Assets      
ARO Underlying Asset $ 0 $ 2