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Segmental Information - Summary of Information by Reportable Segment - Other Segmental Information (Parenthetical) (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure of reportable segments [line items]      
Depreciation and amortisation $ 80 $ 78 $ 75
Administrative expenses [member]      
Disclosure of reportable segments [line items]      
Depreciation and amortisation 61 53 54
Cost of sales [member]      
Disclosure of reportable segments [line items]      
Depreciation and amortisation 19 25 21
System Fund [member]      
Disclosure of reportable segments [line items]      
Depreciation and amortisation $ 45 $ 36 $ 31