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Provisions - Additional Information (Detail)
R / shares in Units, shares in Millions, R in Millions, $ in Millions
 6 Months Ended 12 Months Ended
Dec. 31, 2010
ZAR (R)
R / shares
shares
Dec. 31, 2017
USD ($)
Dec. 31, 2017
ZAR (R)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
 [1]
Dec. 31, 2017
ZAR (R)
Jun. 30, 2017
USD ($)
Disclosure of Provisions [Line Items]              
Class B Ordinary Shares issued / South Deep BEE Transaction | shares 10            
Preferred BEE dividend portion of the South Deep transaction R 151.4            
Equity components R 673.4            
Dividends paid related to south deep BEE dividend   $ 1.5 R 20.0 $ 1.3 [1] $ 1.7    
Current portion of BEE Dividend   1.6   1.4   R 20.0  
Provisions | $   31.9   $ 0.0      
Silicosis [Member]              
Disclosure of Provisions [Line Items]              
Provisions   31.9 R 401.6        
Nominal amount of provision   $ 40.5       R 509.0 $ 40.5
Silicosis [Member] | Government bonds [member]              
Disclosure of Provisions [Line Items]              
Discount rate on government bonds   8.24%       8.24%  
Class B Ordinary Shares Tranche One [Member]              
Disclosure of Provisions [Line Items]              
Percentage of class B Ordinary Shares issued / South Deep BEE Transaction 10.00%            
Dividends per share | R / shares R 2            
Period of conversion for one third Class B Ordinary Shares / South Deep BEE Transaction 10 years            
Class B Ordinary Shares Tranche Two [Member]              
Disclosure of Provisions [Line Items]              
Period of conversion of Class B Ordinary Shares to Class A / South Deep BEE Transaction 20 years            
[1] The restatement is as a result of the discontinued operations.