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Impairment charges - Narrative (Details)
$ in Millions, t in Billions
 6 Months Ended
Jul. 09, 2020
Jul. 16, 2019
USD ($)
Jun. 30, 2020
USD ($)
Jun. 30, 2019
USD ($)
t
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment loss     $ 1,134 $ 2,349
Impairment loss of equity accounted unit     148 0
Property development and project management expense   $ 5,300    
Minimums        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Increase in project expenses   1,200    
Maximums        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Increase in project expenses   $ 1,900    
Investment in equity accounted units ('EAUs')        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment loss     119 0
Pacific Aluminum        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Contract termination notice period 14 months      
Pacific Aluminum | Aluminium, Alumina and Bauxite        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Recoverable amount of asset or cash-generating unit     $ 273  
Discount rate applied to cash flow projections     6.60%  
Impairment loss     $ 489 0
Impairment loss     26  
Pacific Aluminum | Aluminium, Alumina and Bauxite | Pre-tax        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment loss     36  
ISAL | Aluminium, Alumina and Bauxite        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment loss     204 109
Diavik | Copper & Diamonds        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment loss     $ 441 $ 0
Proportion of ownership interest in joint venture (as a percent)     40.00%  
Aluchemie Anode Plant        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Percentage of ownership interest       53.30%
Oyo Tolgoi Copper-Gold Mine        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Recoverable amount of asset or cash-generating unit       $ 8,300
Discount rate applied to cash flow projections       8.30%
Mineral resources | t       2
Recoverable amount, percent       20.00%
Tax Impact of impairment       $ 320
Tax losses expected to expire       $ 359
NCI share of Impairment       66.00%
Rio share of impairment       34.00%
Rio share of impairment, value       $ 800
Oyo Tolgoi Copper-Gold Mine | Minimums        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Production delay period   16 months    
Oyo Tolgoi Copper-Gold Mine | Maximums        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Production delay period   30 months    
Oyo Tolgoi Copper-Gold Mine | Pre-tax        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment loss       2,200
Oyo Tolgoi Copper-Gold Mine | After Tax        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment loss       $ 2,300