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Long-Term Employee Benefit Liabilities - Company's Retirement Medical Benefits Plans (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]    
Non-current liability $ 729 $ 677
Retirement Medical Benefits Plans [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Beginning of year 29 29
Interest cost 1 1
Actuarial losses and changes in actuarial assumptions 1  
Benefits paid (1) (1)
Ending funded status – Plan deficit 30 29
Current liability 1 2
Non-current liability 29 27
Net amount 30 29
Unrecognized actuarial gains 6 11
Total accumulated other comprehensive income 6 11
Interest cost 1 1
Actuarial losses (gains) (1) (1)
Net periodic benefit cost $ 0