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Mining and Income Taxation - Summary of Estimated Available for Set-off Against Future Income Pre Tax (Parenthetical) (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2014
May 30, 2018
South African Revenue Service [Member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Gross recognised capital allowance disallowed     $ 182.2  
Legal settlement amount       $ 185.1
Capital allowance recognized     $ 925.5 $ 53.7
South African - Components of Mining and Income Tax [Member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Gross unredeemed capital expenditure $ 1,641.1 $ 3,143.5    
Abosso Goldfields Limited [member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Tax losses carry forward period Five Years Five Years    
GFI Joint Venture Holdings (Proprietary) Limited [Member] | South African - Components of Mining and Income Tax [Member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Gross unredeemed capital expenditure $ 1,003.1 $ 2,427.1    
Gross recognised capital allowance 1,003.1 925.5    
Gross unrecognised capital allowance 0.0 1,501.6    
Exploration Entities [member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Total tax losses 430.0 445.9    
Tax Losses Expire in 2 Years [Member] | Abosso Goldfields Limited [member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Tax losses 19.0 44.5    
Tax Losses Expire in 3 Years [Member] | Abosso Goldfields Limited [member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Tax losses expiration value 2.9 19.0    
Tax Losses Expire in 4 Years [Member] | Abosso Goldfields Limited [member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Tax losses expiration value 31.5 91.7    
Tax Losses Expire in 5 Years [Member] | Abosso Goldfields Limited [member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Tax losses expiration value 27.5 46.2    
Tax Losses Expiring Between 1 and 2 Years [Member] | Exploration Entities [member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Total tax losses 18.6 22.9    
Tax Losses Expiring Between 2 and 5 Years [Member] | Exploration Entities [member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Total tax losses 27.6 57.6    
Tax Losses Expiring Between 5 and 10 Years [Member] | Exploration Entities [member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Total tax losses 20.3 30.4    
Tax Losses Expiring After 10 Years [Member] | Exploration Entities [member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Total tax losses 42.3 43.2    
No Expiry Date [member] | Exploration Entities [member]        
Disclosure of Estimated Amount Available for Set Off Against Future Income Pretax [Line Items]        
Total tax losses $ 320.9 $ 291.8