v3.26.1
Financial instruments and risk management - Schedule of notional amounts, contractual maturities and rates of hedging instruments designated in hedging relationships by main risk categories (Details)
$ in Millions
Jun. 30, 2026
USD ($)
gBP_per_Metric_Tonnes
poundSterlingPerTherm
Jun. 30, 2025
USD ($)
poundSterlingPerTherm
USD_per_Metric_Tonnes
Net investment hedges | Foreign exchange risk | Derivatives    
Disclosure of detailed information about financial instruments [line items]    
Notional amounts $ 1,704 $ 2,255
Net investment hedges | Foreign exchange risk | Borrowings    
Disclosure of detailed information about financial instruments [line items]    
Notional amounts $ 5,465 $ 9,561
Net investment hedges | Foreign exchange risk | Canadian dollar | Minimum | Derivatives    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 1.32 1.29
Net investment hedges | Foreign exchange risk | Canadian dollar | Maximum | Derivatives    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 1.45 1.48
Net investment hedges | Foreign exchange risk | Chinese yuan | Minimum | Derivatives    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 6.62 6.93
Net investment hedges | Foreign exchange risk | Chinese yuan | Maximum | Derivatives    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 7.29 7.29
Net investment hedges | Foreign exchange risk | Indian rupee | Minimum | Derivatives    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 94.34  
Net investment hedges | Foreign exchange risk | Sterling | Minimum | Borrowings    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.73 0.75
Net investment hedges | Foreign exchange risk | Sterling | Maximum | Borrowings    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.76 0.82
Net investment hedges | Foreign exchange risk | Euro | Minimum | Derivatives    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates   0.84
Net investment hedges | Foreign exchange risk | Euro | Minimum | Borrowings    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.86 0.86
Net investment hedges | Foreign exchange risk | Euro | Maximum | Derivatives    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates   0.85
Net investment hedges | Foreign exchange risk | Euro | Maximum | Borrowings    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.87 0.94
Cash flow hedges | Foreign currency debt risk    
Disclosure of detailed information about financial instruments [line items]    
Notional amounts $ 4,684 $ 2,873
Cash flow hedges | Foreign currency debt risk | Sterling | Minimum    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.74  
Cash flow hedges | Foreign currency debt risk | Sterling | Maximum    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.75  
Cash flow hedges | Foreign currency debt risk | Euro | Minimum    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.87 0.89
Cash flow hedges | Foreign currency debt risk | Euro | Maximum    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.90 0.90
Cash flow hedges | Foreign currency exchange risk    
Disclosure of detailed information about financial instruments [line items]    
Notional amounts $ 1,489 $ 1,586
Cash flow hedges | Foreign currency exchange risk | Sterling | Minimum    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.73 0.74
Cash flow hedges | Foreign currency exchange risk | Sterling | Maximum    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.81 0.81
Cash flow hedges | Foreign currency exchange risk | Mexican peso | Minimum    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 17.95 17.73
Cash flow hedges | Foreign currency exchange risk | Mexican peso | Maximum    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 23.69 23.69
Cash flow hedges | Commodity price risk    
Disclosure of detailed information about financial instruments [line items]    
Notional amounts $ 223 $ 275
Cash flow hedges | Commodity price risk | Minimum | Feed Wheat    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates | gBP_per_Metric_Tonnes 180.00  
Cash flow hedges | Commodity price risk | Minimum | Natural Gas    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates | poundSterlingPerTherm 0.60 0.74
Cash flow hedges | Commodity price risk | Minimum | Aluminium    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates | USD_per_Metric_Tonnes   2,426
Cash flow hedges | Commodity price risk | Maximum | Feed Wheat    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates | gBP_per_Metric_Tonnes 200.00  
Cash flow hedges | Commodity price risk | Maximum | Natural Gas    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates | poundSterlingPerTherm 0.93 1.38
Cash flow hedges | Commodity price risk | Maximum | Aluminium    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates | USD_per_Metric_Tonnes   2,693.5
Fair value hedges | Interest rate risk    
Disclosure of detailed information about financial instruments [line items]    
Notional amounts $ 4,248 $ 4,229
Fair value hedges | Interest rate risk | Minimum | Euro Interbank Offered Rate (EURIBOR)    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.0193 0.0193
Fair value hedges | Interest rate risk | Minimum | Secured Overnight Financing Rate (SOFR)    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.0000 0.0027
Fair value hedges | Interest rate risk | Minimum | Sterling Overnight Index Average    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.0000  
Fair value hedges | Interest rate risk | Maximum | Euro Interbank Offered Rate (EURIBOR)    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.0194 0.0194
Fair value hedges | Interest rate risk | Maximum | Secured Overnight Financing Rate (SOFR)    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.0161 0.0161
Fair value hedges | Interest rate risk | Maximum | Sterling Overnight Index Average    
Disclosure of detailed information about financial instruments [line items]    
Range of hedged rates 0.0014