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Financial instruments and risk management - Summary of Nominal Amount of Bond (Detail)
€ in Millions, £ in Millions, $ in Millions
12 Months Ended
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2020
EUR (€)
Dec. 31, 2020
GBP (£)
Dec. 31, 2019
EUR (€)
Disclosure of detailed information about financial instruments [line items]          
Notional amount $ 1,522 $ 1,656      
Rio Tinto Finance plc Sterling Bonds 4.0% due 2029 | Interest rate swaps          
Disclosure of detailed information about financial instruments [line items]          
Notional amount $ 807     £ 500  
Effective exchange rate 161.32%   161.32% 161.32%  
US Dollar Fixed Rate Borrowings | Interest rate swaps          
Disclosure of detailed information about financial instruments [line items]          
Notional amount $ 5,900 4,500 € 417   € 818
Effective exchange rate 131.05%   131.05% 131.05%  
Change in fair value of the hedging instrument $ 7 (24)      
Change in fair value of the hedged item $ (7) $ 24