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Principal associates - Summary of principal associates (Detail) - shares
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Disclosure of associates [Line Items]      
Rio Tinto Limited shares were held by Rio Tinto plc 0 0 0
Boyne Smelters Limited      
Disclosure of associates [Line Items]      
Country of incorporation of associate Australia    
Principal activities, Associate Aluminium smelting    
Boyne Smelters Limited | Ordinary      
Disclosure of associates [Line Items]      
Company of operation, Associate Boyne Smelters Limited    
Rio Tinto Limited shares were held by Rio Tinto plc 153,679,560    
Proportion of class held (%), Associate 59.40%    
Group interest (%), Associate 59.40%    
Mineracao Rio do Norte S.A.      
Disclosure of associates [Line Items]      
Country of incorporation of associate Brazil    
Principal activities, Associate Bauxite mining    
Group interest (%), Associate 12.00%    
Mineracao Rio do Norte S.A. | Ordinary      
Disclosure of associates [Line Items]      
Rio Tinto Limited shares were held by Rio Tinto plc 25,000,000,000    
Proportion of class held (%), Associate 12.50%    
Mineracao Rio do Norte S.A. | Preferred      
Disclosure of associates [Line Items]      
Company of operation, Associate Mineração Rio do Norte S.A.    
Rio Tinto Limited shares were held by Rio Tinto plc 47,000,000,000    
Proportion of class held (%), Associate 11.75%    
Mineracao Rio do Norte S.A. | Ordinary and Preferred      
Disclosure of associates [Line Items]      
Group interest (%), Associate 12.00%    
Halco (Mining) Inc      
Disclosure of associates [Line Items]      
Country of incorporation of associate US    
Principal activities, Associate Bauxite mining    
Group interest (%), Associate 51.00%    
Halco (Mining) Inc | Common      
Disclosure of associates [Line Items]      
Company of operation, Associate Halco (Mining) Inc.    
Rio Tinto Limited shares were held by Rio Tinto plc 4,500    
Proportion of class held (%), Associate 45.00%    
Group interest (%), Associate 45.00%    
Compagnie des Bauxites de Guine | Halco (Mining) Inc      
Disclosure of associates [Line Items]      
Company of operation, Subsidiary Compagnie des Bauxites de Guinée    
Country of incorporation, Subsidiary Guinea