Postretirement benefits Components of net periodic benefit costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	$ 2	$ 2	$ 6	$ 7
Non-service (benefit) cost	(35)	(31)	(106)	(93)
Net periodic benefit cost (benefit)	(33)	(29)	(100)	(86)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0	0	0
Interest cost	0	0	1	1
Expected return on plan assets	(1)	0	(2)	(2)
Defined Benefit Plan, Amortization of Gain (Loss)	0	(1)	(2)	(2)
Amortization of prior service cost	0	0	0	0
Settlements	0	0	0	0
Non-service (benefit) cost	(1)	(1)	(3)	(3)
Net periodic benefit cost (benefit)	(1)	(1)	(3)	(3)
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	(3)	(3)	(10)	(9)
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	2	6	7
Non-service (benefit) cost	(32)	(28)	(96)	(84)
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)	(3)	(3)
Foreign Plan [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	2	2	6	7
Interest cost	9	9	27	27
Expected return on plan assets	(15)	(13)	(42)	(38)
Defined Benefit Plan, Amortization of Gain (Loss)	1	0	1	1
Amortization of prior service cost	0	0	0	0
Settlements	0	0	0	0
Non-service (benefit) cost	(5)	(4)	(14)	(10)
Net periodic benefit cost (benefit)	(3)	(2)	(8)	(3)
UNITED STATES | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	0	0	0	0
Interest cost	34	33	101	100
Expected return on plan assets	(62)	(61)	(187)	(183)
Defined Benefit Plan, Amortization of Gain (Loss)	(2)	0	(6)	(1)
Amortization of prior service cost	0	0	0	0
Settlements	0	1	0	1
Non-service (benefit) cost	(30)	(27)	(92)	(83)
Net periodic benefit cost (benefit)	$ (30)	$ (27)	$ (92)	$ (83)