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Events after the Reporting Date - Additional Information (Detail)
$ / shares in Units, $ in Millions, ₨ in Billions
 1 Months Ended 12 Months Ended 30 Months Ended
Mar. 23, 2020
USD ($)
Mar. 16, 2020
USD ($)
shares
Feb. 12, 2020
USD ($)
shares
Feb. 12, 2020
INR (₨)
shares
Feb. 12, 2020
R / shares
Apr. 30, 2020
USD ($)
Dec. 31, 2018
USD ($)
shares
Oct. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
May 31, 2018
USD ($)
Dec. 31, 2021
$ / oz
oz
Dec. 31, 2022
CLP ($)
Jul. 01, 2020
USD ($)
Feb. 28, 2020
USD ($)
Dec. 31, 2019
USD ($)
shares
Dec. 31, 2017
USD ($)
 [1]
May 24, 2017
$ / shares
Disclosure of non-adjusting events after reporting period [line items]                                    
Par value | $ / shares                                   $ 0.5
Face amount of borrowings             $ 1,290.0                 $ 1,200.0    
Average strike rate                         836.45          
Cash             219.7                 515.0    
Undrawn borrowing facilities committed             $ 1,097.7 [1]                 $ 1,727.6 $ 1,305.1  
Fair value hedges [member] | Interest rate caps [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Strike price of gold | $ / oz                       2,200            
Currency risk [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Average strike rate             71.5 70.75 71.82 73.3 75.17              
Equity investments [member] | Cardinal Resources Limited [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Asanko Gold Inc. | shares             42,818,182                 81,038,233    
Forward contract [member] | Fair value hedges [member] | Interest rate caps [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Strike price of gold | $ / oz                       2,100            
Forward contract [member] | Currency risk [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Face amount of borrowings             $ 50.0 $ 60.0 $ 100.0 $ 60.0 $ 96.0              
Dividends declared [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Final dividend declared per share | R / shares         R 1                          
Major ordinary share transactions [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Proceeds from issuance of shares     $ 249.0 ₨ 3.7                            
Major ordinary share transactions [member] | Ordinary Shares [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Shares issued during the period | shares     41,431,635 41,431,635                            
Par value | R / shares         R 90.20                          
Environmental Impact Assessment [Member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Capital expenditure           $ 860.0                        
Expected term of capital expenditure           33 months                        
Disposal of equity method [member] | Equity investments [member] | Cardinal Resources Limited [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Asanko Gold Inc. | shares   81,038,233                                
The sale of the shares raised   $ 37.1                                
Entering into average rate forwards [member] | Forward contract [member] | Currency risk [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Face amount of borrowings                           $ 544.5        
Entering into asian puts [member] | Fair value hedges [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Volume of gold hedged | oz                       100,000.00            
Entering into asian puts [member] | Forward contract [member] | Fair value hedges [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Volume of gold hedged | oz                       200,000.00            
Advances payment to contractor [member] | Mining contractor [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Advance to suppliers                             $ 68.0      
Advances paid $ 62.0                                  
Non Adjusting Event [member]                                    
Disclosure of non-adjusting events after reporting period [line items]                                    
Cash 600.0                                  
Undrawn borrowing facilities committed $ 1,500.0                                  
[1] Refer note 42.