Postretirement benefits Components of net periodic benefit costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	$ 2	$ 2
Non-service (benefit) cost	(47)	(35)
Net periodic benefit cost (benefit)	(45)	(33)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0
Interest cost	0	0
Expected return on plan assets	0	0
Defined Benefit Plan, Amortization of Gain (Loss)	0	(1)
Amortization of prior service cost	0	0
Settlements	0	0
Non-service (benefit) cost	0	(1)
Net periodic benefit cost (benefit)	0	(1)
Losses and loss expenses | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0
Non-service (benefit) cost	(4)	(3)
Losses and loss expenses | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0
Non-service (benefit) cost	0	0
Administrative Expense | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	2	2
Non-service (benefit) cost	(43)	(32)
Administrative Expense | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0
Non-service (benefit) cost	0	(1)
Foreign Plan [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	2	2
Interest cost	9	9
Expected return on plan assets	(16)	(13)
Defined Benefit Plan, Amortization of Gain (Loss)	0	0
Amortization of prior service cost	0	0
Settlements	0	0
Non-service (benefit) cost	(7)	(4)
Net periodic benefit cost (benefit)	(5)	(2)
UNITED STATES | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0
Interest cost	31	34
Expected return on plan assets	(68)	(63)
Defined Benefit Plan, Amortization of Gain (Loss)	(3)	(2)
Amortization of prior service cost	0	0
Settlements	0	0
Non-service (benefit) cost	(40)	(31)
Net periodic benefit cost (benefit)	$ (40)	$ (31)