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Financial Instruments and Risk Management (Credit Risk - Movement in the Allowance of Doubtful Accounts during the Year) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Notes to Consolidated Financial Statements [Abstract]    
Balance at start of period $ 3 $ 3
Additional allowance 5 2
Write offs 0 (1)
Reversals 0 (1)
Change due to translation differences 2 0
Balance at end of period $ 10 $ 3