v3.24.0.1
Introduction and overview of Group's risk management - Sensitivity analysis (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Introduction and overview of Group's risk management      
Export sales $ 0    
Foreign exchange risk | Euro      
Introduction and overview of Group's risk management      
Rate of change 10.00% 7.00% 5.00%
Effect of US Dollar weakening on loss $ (21,911) $ (13,153) $ (15,726)
Effect of US Dollar strengthening on loss $ 21,911 $ 13,153 $ 15,726
Foreign exchange risk | Rwandan Franc      
Introduction and overview of Group's risk management      
Rate of change 10.00% 7.00% 5.00%
Effect of US Dollar weakening on loss $ (1,311) $ (4,402) $ (3,284)
Effect of US Dollar strengthening on loss $ 1,311 $ 4,402 $ 3,284
Foreign exchange risk | Nigeria Naira      
Introduction and overview of Group's risk management      
Rate of change 10.00% 7.00% 5.00%
Effect of US Dollar weakening on loss $ (255,956) $ (165,880) $ (106,595)
Effect of US Dollar strengthening on loss $ 255,956 $ 165,880 $ 106,595
Foreign exchange risk | Zambian Kwacha      
Introduction and overview of Group's risk management      
Rate of change 10.00% 7.00% 5.00%
Effect of US Dollar weakening on loss $ (16,038) $ (15,528) $ (11,078)
Effect of US Dollar strengthening on loss $ 16,038 $ 15,528 $ 11,078
Foreign exchange risk | South Africa, Rand      
Introduction and overview of Group's risk management      
Rate of change 10.00% 7.00%  
Effect of US Dollar weakening on loss $ (3,996) $ (2,809)  
Effect of US Dollar strengthening on loss $ 3,996 $ 2,809  
Foreign exchange risk | Brazil Real      
Introduction and overview of Group's risk management      
Rate of change 10.00% 7.00% 5.00%
Effect of US Dollar weakening on loss   $ (18,898) $ (15,502)
Effect of US Dollar strengthening on loss   $ 18,898 $ 15,502
Foreign exchange risk | Kuwaiti Dinar      
Introduction and overview of Group's risk management      
Rate of change 10.00% 7.00% 5.00%
Effect of US Dollar weakening on loss $ (1,047) $ (648) $ (424)
Effect of US Dollar strengthening on loss $ 1,047 $ 648 $ 424