v3.26.1
Post employment benefits - Sensitivity analyses of potential impacts on consolidated income statement and on plan liabilities (Details)
$ in Millions
 12 Months Ended
Jun. 30, 2026
USD ($)
yr
Jun. 30, 2025
USD ($)
Jun. 30, 2024
USD ($)
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit $ 3,156 $ 4,335 $ 6,001
Profit for the year $ 1,958 $ 2,538 $ 4,166
Discount rate      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Percentage of reasonably possible increase in actuarial assumption 0.50%    
Percentage of reasonably possible decrease in actuarial assumption 0.50%    
Inflation      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Percentage of reasonably possible increase in actuarial assumption 0.50%    
Percentage of reasonably possible decrease in actuarial assumption 0.50%    
Life expectancy      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Duration of reasonably possible increase in actuarial assumption | yr 1    
United Kingdom | Effect of 0.5% increase in discount rate      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit $ 2    
Profit for the year 14    
Plan liabilities 229    
United Kingdom | Effect of 0.5% decrease in discount rate      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit (2)    
Profit for the year (13)    
Plan liabilities (250)    
United Kingdom | Effect of 0.5% increase in inflation      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit (2)    
Profit for the year (8)    
Plan liabilities (157)    
United Kingdom | Effect of 0.5% decrease in inflation      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit 1    
Profit for the year 7    
Plan liabilities 148    
United Kingdom | Effect of one year increase in life expectancy      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit 0    
Profit for the year (6)    
Plan liabilities (129)    
Ireland | Effect of 0.5% increase in discount rate      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit 1    
Profit for the year 6    
Plan liabilities 85    
Ireland | Effect of 0.5% decrease in discount rate      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit (1)    
Profit for the year (5)    
Plan liabilities (94)    
Ireland | Effect of 0.5% increase in inflation      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit 0    
Profit for the year (2)    
Plan liabilities (36)    
Ireland | Effect of 0.5% decrease in inflation      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit 0    
Profit for the year 2    
Plan liabilities 36    
Ireland | Effect of one year increase in life expectancy      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit 0    
Profit for the year (3)    
Plan liabilities (60)    
United States | Effect of 0.5% increase in discount rate      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit 2    
Profit for the year 2    
Plan liabilities 27    
United States | Effect of 0.5% decrease in discount rate      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit (2)    
Profit for the year (2)    
Plan liabilities (30)    
United States | Effect of 0.5% increase in inflation      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit 0    
Profit for the year (1)    
Plan liabilities (9)    
United States | Effect of 0.5% decrease in inflation      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit 0    
Profit for the year 1    
Plan liabilities 9    
United States | Effect of one year increase in life expectancy      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Operating profit 0    
Profit for the year (1)    
Plan liabilities $ (17)