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Operating segments - Summary of depreciation and amortisation within the reportable segments (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure of operating segments [Line Items]      
Depreciation and amortisation expense proportionately consolidated $ 4,015 $ 4,375 $ 4,794
Reportable segments [Member] | Iron Ore [Member]      
Disclosure of operating segments [Line Items]      
Depreciation and amortisation expense proportionately consolidated 1,682 1,645 1,645
Reportable segments [Member] | Aluminium [Member]      
Disclosure of operating segments [Line Items]      
Depreciation and amortisation expense proportionately consolidated 1,122 1,199 1,250
Reportable segments [Member] | Copper & Diamonds [member]      
Disclosure of operating segments [Line Items]      
Depreciation and amortisation expense proportionately consolidated 1,317 1,452 1,601
Reportable segments [Member] | Energy & Minerals [Member]      
Disclosure of operating segments [Line Items]      
Depreciation and amortisation expense proportionately consolidated 475 652 739
Reportable segments [Member] | Other operations [Member]      
Disclosure of operating segments [Line Items]      
Depreciation and amortisation expense proportionately consolidated 26 32 34
Product group [Member]      
Disclosure of operating segments [Line Items]      
Depreciation and amortisation expense proportionately consolidated 4,622 4,980 5,269
Other items [Member]      
Disclosure of operating segments [Line Items]      
Depreciation and amortisation expense proportionately consolidated 43 42 51
Depreciation and amortisation of equity accounted units [Member]      
Disclosure of operating segments [Line Items]      
Depreciation and amortisation expense proportionately consolidated $ (650) $ (647) $ (526)