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Equity-Accounted Investees - Summary of Equity-Accounted Investees (Parenthetical) (Detail) - USD ($)
$ in Millions
 12 Months Ended
Mar. 29, 2018
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2016
Dec. 31, 2017
Disclosure of equity-accounted investees [line items]            
Total investment in joint venture   $ 233.3 $ 172.0      
cash and cash equivalents includes in cash and cash equivalents   886.8 515.0 $ 219.7   $ 393.8
Profit on disposal   (0.2) 1.2 $ (51.6)    
Rusoro Mining Limited ("Rusoro")   233.3 172.0      
Investment in associate   0.0 0.0      
Property, plant and equipment   4,771.2 4,657.1      
Asanko Gold Ghana Limited [member]            
Disclosure of equity-accounted investees [line items]            
Interest on joint venture 45.00%          
Government of Ghana ownership retained 10.00%          
cash and cash equivalents includes in cash and cash equivalents   $ 64.3 43.7      
Shika Group Finance Limited [member]            
Disclosure of equity-accounted investees [line items]            
Interest on joint venture 50.00%          
Adansi Gold Company Ghana Limited [member]            
Disclosure of equity-accounted investees [line items]            
Interest on joint venture 50.00%          
FSE [member]            
Disclosure of equity-accounted investees [line items]            
Remaining percentage of ownership not yet exercised   20.00%        
Unlisted shares at cost   $ 230.0 230.0      
Equity contribution   95.2 93.6      
Cumulative impairment   (85.6) (147.9)      
Share of accumulated losses brought forward   (93.6) (92.2)      
Share of loss after taxation   (1.6) (1.4)      
Total investment in joint venture   $ 144.4 $ 82.1      
Interest on joint venture   40.00% 40.00% 40.00%    
Asanko Gold [member]            
Disclosure of equity-accounted investees [line items]            
Share of accumulated losses brought forward   $ 3.0 $ (1.1)      
Total investment in joint venture   88.9 $ 89.9      
Property, plant and equipment   39.6        
Asanko Gold [member] | Impairment Trigger During 2020 [member]            
Disclosure of equity-accounted investees [line items]            
Impairment loss recognised in Join venture   $ 49.5        
Marverix Metals Incorporated [member]            
Disclosure of equity-accounted investees [line items]            
Common Shares         42,850,000  
Common shares   4,125,000 4,125,000   10,000,000  
Common shares issued       60,000,000    
Common shares purchase warrants       10,000,000    
Interest on listed entity   0.00% 0.00%      
Profit on disposal     $ 14.6 $ 4.0 $ 48.0  
Listed shares at cost   $ 0.0 42.1      
Profit on dilution of Gold Fields' interest in Maverix   0.0 4.0      
Transaction costs capitalised   0.0 0.3      
Share of accumulated profits brought forward   0.0 1.2      
Share of profit after taxation   0.0 0.4      
Derecognition of associate   0.0 (48.0)      
Investment in associate   $ 0.0 $ 0.0      
Marverix Metals Incorporated [member] | Top of range [member]            
Disclosure of equity-accounted investees [line items]            
Interest on listed entity       28.00%    
Marverix Metals Incorporated [member] | Bottom of range [member]            
Disclosure of equity-accounted investees [line items]            
Interest on listed entity       20.00%    
Rusoro Mining Limited [member]            
Disclosure of equity-accounted investees [line items]            
Percentage of remaining shares   25.70% 25.70%      
Rusoro Mining Limited ("Rusoro")   $ 0.0 $ 0.0