Postretirement benefits Components of net periodic benefit costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	$ 2	$ 3	$ 4	$ 5
Non-service (benefit) cost	(36)	(31)	(71)	(62)
Net periodic benefit cost (benefit)	(34)	(28)	(67)	(57)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0	0	0
Interest cost	1	0	1	1
Expected return on plan assets	(1)	(1)	(1)	(2)
Defined Benefit Plan, Amortization of Gain (Loss)	(1)	0	(2)	(1)
Amortization of prior service cost	0	0	0	0
Settlements	0	0	0	0
Non-service (benefit) cost	(1)	(1)	(2)	(2)
Net periodic benefit cost (benefit)	(1)	(1)	(2)	(2)
Losses and loss expenses | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0	0	0
Non-service (benefit) cost	(4)	(3)	(7)	(6)
Losses and loss expenses | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0	0	0
Non-service (benefit) cost	0	0	0	0
Administrative Expense | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	2	3	4	5
Non-service (benefit) cost	(32)	(28)	(64)	(56)
Administrative Expense | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0	0	0
Non-service (benefit) cost	(1)	(1)	(2)	(2)
Foreign Plan [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	2	3	4	5
Interest cost	9	9	18	18
Expected return on plan assets	(14)	(12)	(27)	(25)
Defined Benefit Plan, Amortization of Gain (Loss)	0	0	0	1
Amortization of prior service cost	0	0	0	0
Settlements	0	0	0	0
Non-service (benefit) cost	(5)	(3)	(9)	(6)
Net periodic benefit cost (benefit)	(3)	0	(5)	(1)
UNITED STATES | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0	0	0
Interest cost	33	34	67	67
Expected return on plan assets	(62)	(61)	(125)	(122)
Defined Benefit Plan, Amortization of Gain (Loss)	(2)	(1)	(4)	(1)
Amortization of prior service cost	0	0	0	0
Settlements	0	0	0	0
Non-service (benefit) cost	(31)	(28)	(62)	(56)
Net periodic benefit cost (benefit)	$ (31)	$ (28)	$ (62)	$ (56)