v3.26.1
Post employment benefits - Timing of benefit payments and average duration of defined benefit obligations and distribution of timing of benefit payments (Details) - USD ($)
$ in Millions
 12 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid $ 0 $ 0
United Kingdom    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid $ 10,600 $ 10,957
Average duration of the defined benefit obligation 11 years 12 years
United Kingdom | Within one year    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid $ 356 $ 375
United Kingdom | Between 1 to 5 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid 1,410 1,430
United Kingdom | Between 6 to 15 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid 3,416 3,472
United Kingdom | Between 16 to 25 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid 2,920 2,986
United Kingdom | Beyond 25 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid 2,498 2,694
Ireland    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid $ 2,890 $ 2,978
Average duration of the defined benefit obligation 12 years 13 years
Ireland | Within one year    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid $ 107 $ 100
Ireland | Between 1 to 5 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid 510 478
Ireland | Between 6 to 15 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid 910 912
Ireland | Between 16 to 25 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid 691 745
Ireland | Beyond 25 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid 672 743
United States    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid $ 1,399 $ 1,319
Average duration of the defined benefit obligation 9 years 9 years
United States | Within one year    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid $ 71 $ 68
United States | Between 1 to 5 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid 226 215
United States | Between 6 to 15 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid 500 476
United States | Between 16 to 25 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid 337 315
United States | Beyond 25 years    
Disclosure of defined benefit plans [line items]    
Benefits expected to be paid $ 265 $ 245