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Borrowings and other financial liabilities - Additional information (Detail) - USD ($)
Dec. 31, 2018
Dec. 31, 2017
Disclosure of detailed information about borrowings [Line Items]    
Derivative financial assets $ 556,000,000 $ 267,000,000
Derivative financial liabilities (502,000,000) (531,000,000)
Interest rate swaps [member]    
Disclosure of detailed information about borrowings [Line Items]    
Derivative financial liabilities 358,000,000 276,000,000
Rio Tinto Finance (USA) Limited Bonds 7.125% 2028 [member]    
Disclosure of detailed information about borrowings [Line Items]    
Borrowings at amortised cost 75,000,000 75,000,000
Interest rate swaps [member]    
Disclosure of detailed information about borrowings [Line Items]    
Derivative financial assets 70,000,000 99,000,000
Cross currency interest rate swaps [member] | Rio Tinto Finance plc Sterling Bonds 4.0% due 2029 [member]    
Disclosure of detailed information about borrowings [Line Items]    
Borrowings notional amount 600,000,000 700,000,000
US Dollars [Member] | Interest rate swaps [member]    
Disclosure of detailed information about borrowings [Line Items]    
Borrowings notional amount 4,300,000,000 5,700,000,000
Euro Member Countries, Euro | Interest rate swaps [member]    
Disclosure of detailed information about borrowings [Line Items]    
Borrowings notional amount $ 900,000,000 $ 1,500,000,000