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Commitments and Contingent Liabilities - Summary of Asset Retirement Obligations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Balance at January 1, $ 76 $ 66
Obligations incurred or acquired 12 5
(Decrease) increase in estimated cash outflows (14) 4
Accretion expense 4 4
Settlements and payments (2) (3)
Balance at December 31, 76 76
Current portion 13 7
Non-current portion $ 63 $ 69