XML 169 R162.htm IDEA: XBRL DOCUMENT v3.8.0.1
Trade and other receivables - Summary of ageing receivables (Detail) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Disclosure Of Aging Of Trade And Other Receivables Past Due But Not Impaired [Line Items]    
Trade receivables $ 2,315 $ 2,283
Trade receivables past due but not impaired [Member]    
Disclosure Of Aging Of Trade And Other Receivables Past Due But Not Impaired [Line Items]    
Trade receivables 145 230
Trade receivables past due but not impaired [Member] | Less than 30 days overdue [member]    
Disclosure Of Aging Of Trade And Other Receivables Past Due But Not Impaired [Line Items]    
Trade receivables 122 196
Trade receivables past due but not impaired [Member] | Between 30 and 60 days overdue [member]    
Disclosure Of Aging Of Trade And Other Receivables Past Due But Not Impaired [Line Items]    
Trade receivables 3 4
Trade receivables past due but not impaired [Member] | Between 60 and 90 days overdue [member]    
Disclosure Of Aging Of Trade And Other Receivables Past Due But Not Impaired [Line Items]    
Trade receivables 17 7
Trade receivables past due but not impaired [Member] | More than 90 days overdue [member]    
Disclosure Of Aging Of Trade And Other Receivables Past Due But Not Impaired [Line Items]    
Trade receivables $ 3 $ 23