Financial risk management activities - Reconciliation of deferred compensation asset (Details) - USD ($) $ in Millions |
6 Months Ended | 12 Months Ended | |
|---|---|---|---|
Jun. 30, 2026 |
Dec. 31, 2025 |
Jun. 30, 2025 |
|
| Deferred Compensation Asset [Roll Forward] | |||
| Opening balance | $ 122 | $ 48 | |
| Changes in estimates - fair value adjustments | 8 | 13 | |
| Contingent consideration assets recognised on sale of business | 0 | 78 | |
| Part repayment of contingent consideration asset - Mponeng and MSG | (19) | (19) | |
| Translation | 1 | 2 | |
| Closing balance | 112 | 122 | |
| Contingent considerations | 40 | 62 | $ 62 |
| Contingent consideration | $ 72 | $ 60 | $ 60 |