Retirement benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 0	$ 0
Interest cost	1	1
Expected return on plan assets	0	0
Amortization of prior service cost	0	0
Amortization of net actuarial loss (gain)	(1)	0
Net periodic benefit cost (income)	0	1
United States | Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	6	7
Interest cost	42	46
Expected return on plan assets	(58)	(61)
Amortization of prior service cost	1	1
Amortization of net actuarial loss (gain)	1	2
Net periodic benefit cost (income)	(8)	(5)
Non-U.S. Pension Benefits | Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	6	6
Interest cost	18	19
Expected return on plan assets	(23)	(22)
Amortization of prior service cost	0	0
Amortization of net actuarial loss (gain)	2	2
Net periodic benefit cost (income)	$ 3	$ 5