XML 223 R195.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Financial instruments and risk management - Credit risk - Additional information (Detail)
 12 Months Ended
Dec. 31, 2019
USD ($)
Customer
Dec. 31, 2018
USD ($)
Customer
Commodity price risk [Member]    
Disclosure of detailed information about financial instruments [line items]    
Description of hedging strategy Rio Tinto’s exposure to commodity prices is diversified by virtue of its broad commodity base and the Group does not generally consider that commodity fixed price hedging would provide a long-term benefit to shareholders.  
Credit risk [member]    
Disclosure of detailed information about financial instruments [line items]    
Description of customers receivable owing The Group had approximately 113 customers (2017: 115 customers) that owed the Group more than US$5 million each and these balances accounted for approximately 84% (2017: 78%) of all trade receivables. There were 17 customers (2017: 23 customers) with balances greater than US$20 million accounting for just over 34% (2017: 35%) of all trade receivables.  
Credit risk [member] | More than US dollar 5 million    
Disclosure of detailed information about financial instruments [line items]    
Number of customers | Customer 78 113
Per cent of trade receivables 90.00% 84.00%
Credit risk [member] | Greater than US dollar 20 million    
Disclosure of detailed information about financial instruments [line items]    
Number of customers | Customer 22 17
Per cent of trade receivables 55.00% 34.00%
Foreign exchange risk    
Disclosure of detailed information about financial instruments [line items]    
Description of hedging strategy Under normal market conditions, the Group does not consider that active currency hedging of transactions would provide long-term benefits to shareholders. The Group reviews its exposure on a regular basis and will undertake hedging if deemed appropriate. Currency protection measures may be deemed appropriate in specific commercial circumstances. Capital expenditures and other significant financial items such as acquisitions, disposals, tax and dividend cash flows may be hedged subject to strict limits laid down by the board. Refer to section B for details of the cross-currency interest rate swaps, and the currency forward and option contracts used to manage the currency risk exposures  
Interest rate swaps [Member] | Credit risk [member] | More than US dollar 5 million    
Disclosure of detailed information about financial instruments [line items]    
Amount of receivable held at year end (more than) $ 5,000,000  
Interest rate swaps [Member] | Credit risk [member] | Greater than US dollar 20 million    
Disclosure of detailed information about financial instruments [line items]    
Amount of receivable held at year end (more than)   $ 20,000,000
Fair value hedges [member] | Foreign exchange risk    
Disclosure of detailed information about financial instruments [line items]    
Hedged item, assets 151,000,000 70,000,000
Hedged item, liabilities $ 298,000,000 $ 358,000,000