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Contingent Liabilities - Additional Information (Detail)
$ in Millions
Dec. 31, 2020
USD ($)
Dec. 31, 2020
ZAR (R)
Dec. 31, 2019
USD ($)
Dec. 31, 2019
ZAR (R)
Dec. 31, 2018
USD ($)
Dec. 31, 2018
ZAR (R)
Disclosure of contingent liabilities [line items]            
Provisions | $ $ 18.3   $ 21.2   $ 25.1  
Silicosis [Member]            
Disclosure of contingent liabilities [line items]            
Provisions 18.3 R 268,600,000 $ 21.2 R 297,100,000    
Nominal amount of provision $ 23.1 339,300,000        
Settlement payment for silicosis   R 250,000        
Alleged thefts [Member] | Randgold and Exploration Summons [Member]            
Disclosure of contingent liabilities [line items]            
Amount of summons claims computed pursuant to allegedly received           R 43,700,000,000
Based On Value Of Shares [Member] | Alleged thefts [Member] | Randgold and Exploration Summons [Member]            
Disclosure of contingent liabilities [line items]            
Amount of summons claims computed pursuant to allegedly received           R 26,900,000,000