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Goodwill - Additional information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Richards Bay Minerals    
Disclosure of reconciliation of changes in goodwill [Line Items]    
Impairment charges $ 0 $ 0
Fair value less costs of disposal, post-tax discount rate 8.60% 8.60%
Pilbara    
Disclosure of reconciliation of changes in goodwill [Line Items]    
Fair value less costs of disposal, post-tax discount rate 6.60% 6.60%