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Commitments and Contingent Liabilities - Summary of Asset Retirement Obligations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Balance at January 1, $ 57 $ 48
Accretion expense 7 10
Settlements and payments (3) (1)
Balance at December 31, 61 57
Current portion 7 6
Non-current portion $ 54 $ 51