Financial instruments and risk management - Commodity price sensitivity and hedging (Details)	Dec. 31, 2025 oz $ / t t $ / oz	Dec. 09, 2024 R / oz oz	Nov. 04, 2024 R / oz oz	May 03, 2023 R / oz oz	Nov. 30, 2021 t	Jun. 15, 2021 oz
Zinc
Foreign currency sensitivity analysis
Quantity of hedged instrument (in tonne/ounce)					90,000	90,000
Zinc \| Commodity price risk \| Within one year \| Hedging instrument 1
Foreign currency sensitivity analysis
Quantity of hedged instrument (in tonne/ounce) \| t	3,300
Zinc \| Commodity price risk \| Within one year \| Hedging instrument 2
Foreign currency sensitivity analysis
Quantity of hedged instrument (in tonne/ounce) \| t	6,000
Zinc \| Commodity price risk \| Within one year \| Hedging instrument 3
Foreign currency sensitivity analysis
Quantity of hedged instrument (in tonne/ounce) \| t	2,700
Zinc \| Commodity price risk \| Within one year \| Hedging Instrument 4
Foreign currency sensitivity analysis
Quantity of hedged instrument (in tonne/ounce) \| t	12,000
Zinc \| Minimum \| Commodity price risk \| Within one year \| Hedging instrument 1
Foreign currency sensitivity analysis
Average price (in ZAR/AUD per ounce/tonne)	4,250
Zinc \| Minimum \| Commodity price risk \| Within one year \| Hedging instrument 2
Foreign currency sensitivity analysis
Average price (in ZAR/AUD per ounce/tonne)	4,200
Zinc \| Minimum \| Commodity price risk \| Within one year \| Hedging instrument 3
Foreign currency sensitivity analysis
Average price (in ZAR/AUD per ounce/tonne)	4,250
Zinc \| Minimum \| Commodity price risk \| Within one year \| Hedging Instrument 4
Foreign currency sensitivity analysis
Average price (in ZAR/AUD per ounce/tonne)	4,300
Zinc \| Maximum \| Commodity price risk \| Within one year \| Hedging instrument 1
Foreign currency sensitivity analysis
Average price (in ZAR/AUD per ounce/tonne)	4,800
Zinc \| Maximum \| Commodity price risk \| Within one year \| Hedging instrument 2
Foreign currency sensitivity analysis
Average price (in ZAR/AUD per ounce/tonne)	4,750
Zinc \| Maximum \| Commodity price risk \| Within one year \| Hedging instrument 3
Foreign currency sensitivity analysis
Average price (in ZAR/AUD per ounce/tonne)	4,800
Zinc \| Maximum \| Commodity price risk \| Within one year \| Hedging Instrument 4
Foreign currency sensitivity analysis
Average price (in ZAR/AUD per ounce/tonne)	4,900
Gold
Foreign currency sensitivity analysis
Quantity of hedged instrument (in tonne/ounce) \| oz		168,000	182,000	154,320
Gold \| Commodity price risk \| Within one year
Foreign currency sensitivity analysis
Quantity of hedged instrument (in tonne/ounce) \| oz	3,400
Average price (in ZAR/AUD per ounce/tonne) \| $ / oz	4,206
Gold \| Minimum
Foreign currency sensitivity analysis
Average price (in ZAR/AUD per ounce/tonne) \| R / oz		45,000	45,000	34,214
Gold \| Maximum
Foreign currency sensitivity analysis
Average price (in ZAR/AUD per ounce/tonne) \| R / oz		54,400	58,500	46,050
Silver \| Commodity price risk \| Within one year
Foreign currency sensitivity analysis
Quantity of hedged instrument (in tonne/ounce) \| oz	195,000
Average price (in ZAR/AUD per ounce/tonne) \| $ / oz	57
Platinum \| Commodity price risk \| Within one year
Foreign currency sensitivity analysis
Quantity of hedged instrument (in tonne/ounce) \| oz	5,850
Average price (in ZAR/AUD per ounce/tonne) \| $ / oz	1,918
Paladium \| Commodity price risk \| Within one year
Foreign currency sensitivity analysis
Quantity of hedged instrument (in tonne/ounce) \| oz	9,600
Average price (in ZAR/AUD per ounce/tonne) \| $ / oz	1,501