v3.26.1
Segment reporting - Summarized segment assets and liabilities and additions (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Disclosure of operating segments [line items]          
Segment assets $ 4,360.0   $ 4,360.0   $ 4,489.6
Total liabilities 4,542.6   4,542.6   $ 4,579.4
Additions of property, plant and equipment, right of use assets and intangible assets 62.5 $ 84.1 109.8 $ 140.9  
Operating segments          
Disclosure of operating segments [line items]          
Additions of property, plant and equipment, right of use assets and intangible assets 62.9 84.1 110.2 140.5  
Unallocated items          
Disclosure of operating segments [line items]          
Additions of property, plant and equipment, right of use assets and intangible assets (0.4)   (0.4) 0.4  
Nigeria | Operating segments          
Disclosure of operating segments [line items]          
Additions of property, plant and equipment, right of use assets and intangible assets 25.1 17.0 42.5 18.6  
SSA | Operating segments          
Disclosure of operating segments [line items]          
Additions of property, plant and equipment, right of use assets and intangible assets 8.2 19.4 16.6 38.1  
Latam | Operating segments          
Disclosure of operating segments [line items]          
Additions of property, plant and equipment, right of use assets and intangible assets $ 29.6 $ 47.7 $ 51.1 $ 83.8