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Asset Retirement Obligations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Asset retirement obligations    
Balance at beginning of year $ 556 $ 524
Additional liabilities accrued 25 10
Revisions in estimated cash outflows 9 (3)
Disposition of assets (11) (4)
Accretion expense 29 29
Balance at end of year $ 608 $ 556