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Asset Retirement Obligations - PAC - Change in Asset Retirement Obligations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning Balance $ 1,341 $ 1,272
Change in estimated costs 81 46
Additions 15 51
Retirements (144) (201)
Accretion 47 51
Ending Balance 1,340 1,341
Current liabilities 130 184
Other long-term liabilities 1,210 1,157
Total ARO liability 1,340 1,341
PAC    
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning Balance 270 257
Change in estimated costs 40 (11)
Additions 0 25
Retirements (15) (10)
Accretion 9 9
Ending Balance 304 270
Current liabilities 5 13
Other long-term liabilities 299 257
Total ARO liability $ 304 $ 270