XML 115 R81.htm IDEA: XBRL DOCUMENT v3.22.0.1
Asset Retirement Obligations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Asset retirement obligations    
Balance at beginning of year $ 377 $ 342
Additional liabilities accrued 28 5
Revisions in estimated cash outflows 42 11
Disposition of assets (1) (1)
Accretion expense 23 20
Balance at end of year $ 469 $ 377