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Risk Management Activities - Summary of Effect of Change in Finance Expense on Group's Profit or Loss had LIBOR and Prime Differed as Indicated (Detail)
 12 Months Ended
Dec. 31, 2022
USD ($)
ExchangeRates
Dec. 31, 2021
USD ($)
ExchangeRates
Dec. 31, 2020
Rand      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Closing exchange rate 17.02 15.94 14.69
Average exchange rate 16.37 14.79 16.38
Closing foreign exchange rate | Rand      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Closing exchange rate | ExchangeRates 17.02 15.94  
Sensitivity to BBSY interest rates | Closing foreign exchange rate      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Average exchange rate 0.69 0.75  
-0.1      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
(Decrease)/increase in OCI $ (3,500,000) $ (3,100,000)  
-0.05      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
(Decrease)/increase in OCI (1,700,000) (1,500,000)  
Increase/(decrease) in OCI 10,100,000    
0.05      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
(Decrease)/increase in OCI 1,700,000 1,500,000  
Increase/(decrease) in OCI (8,000,000.0)    
0.1      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
(Decrease)/increase in OCI 3,500,000 3,100,000  
-0.025      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Increase/(decrease) in OCI 4,700,000    
0.025      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Increase/(decrease) in OCI (4,200,000)    
-0.01      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Increase/(decrease) in OCI   3,500,000  
-0.01 | Sensitivity to interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense (1,600,000) (3,300,000)  
-0.01 | Sensitivity to interest rates | Sensitivity to LIBOR interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense (800,000) (1,500,000)  
-0.01 | Sensitivity to interest rates | Sensitivity to BBSY interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense (800,000) (1,800,000)  
-0.02      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Increase/(decrease) in OCI   7,100,000  
0.02      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Increase/(decrease) in OCI   (6,500,000)  
0.01      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Increase/(decrease) in OCI   (3,300,000)  
0.01 | Sensitivity to interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense 1,600,000 3,300,000  
0.01 | Sensitivity to interest rates | Sensitivity to LIBOR interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense 800,000 1,500,000  
0.01 | Sensitivity to interest rates | Sensitivity to BBSY interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense 800,000 1,800,000  
1 year earlier      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Increase/(decrease) in OCI 10,300,000 8,500,000  
1 year later      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Increase/(decrease) in OCI (10,900,000) (7,800,000)  
-0.015 | Sensitivity to interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense (2,500,000) (4,900,000)  
-0.015 | Sensitivity to interest rates | Sensitivity to LIBOR interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense (1,300,000) (2,200,000)  
-0.015 | Sensitivity to interest rates | Sensitivity to BBSY interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense (1,200,000) (2,700,000)  
-0.005 | Sensitivity to interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense (800,000) (1,600,000)  
-0.005 | Sensitivity to interest rates | Sensitivity to LIBOR interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense (400,000) (700,000)  
-0.005 | Sensitivity to interest rates | Sensitivity to BBSY interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense (400,000) (900,000)  
0.005 | Sensitivity to interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense 800,000 1,600,000  
0.005 | Sensitivity to interest rates | Sensitivity to LIBOR interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense 400,000 700,000  
0.005 | Sensitivity to interest rates | Sensitivity to BBSY interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense 400,000 900,000  
0.015 | Sensitivity to interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense 2,500,000 4,900,000  
0.015 | Sensitivity to interest rates | Sensitivity to LIBOR interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense 1,300,000 2,200,000  
0.015 | Sensitivity to interest rates | Sensitivity to BBSY interest rates      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Change in finance expense $ 1,200,000 $ 2,700,000