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Asset Retirement Obligations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Asset retirement obligations    
Balance at beginning of year $ 524 $ 469
Additional liabilities accrued 10 19
Revisions in estimated cash outflows (3) 11
Disposition of assets (4) (1)
Accretion expense 29 26
Balance at end of year $ 556 $ 524