Postemployment benefit plans - Components of net periodic benefit cost, amounts recognized in OCI, weighted average assumptions used to determine net periodic benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Components of net periodic benefit cost:
Net periodic benefit cost (benefit)	$ 67	$ (65)	$ 916
Pension Plan | U.S. Pension Benefits
Components of net periodic benefit cost:
Service cost	0	0	0
Interest cost	625	656	401
Expected return on plan assets	(699)	(689)	(669)
Curtailments, settlements and termination benefits	0	0	0
Amortization of prior service cost (credit)	0	0	0
Actuarial loss (gain)	0	(138)	259
Net periodic benefit cost (benefit)	(74)	(171)	(9)
Amounts recognized in other comprehensive income (pre-tax):
Current year prior service cost (credit)	0	0	0
Amortization of prior service (cost) credit	0	0	0
Total recognized in other comprehensive income	0	0	0
Total recognized in net periodic cost and other comprehensive income	$ (74)	$ (171)	$ (9)
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate used to measure service cost	0.00%	0.00%	0.00%
Discount rate used to measure interest cost	5.00%	5.20%	2.30%
Expected rate of return on plan assets	5.70%	5.80%	4.00%
Rate of compensation increase	0.00%	0.00%	0.00%
Pension Plan | Non-U.S.  Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 43	$ 40	$ 50
Interest cost	118	124	69
Expected return on plan assets	(165)	(163)	(130)
Curtailments, settlements and termination benefits	0	1	1
Amortization of prior service cost (credit)	0	0	0
Actuarial loss (gain)	59	172	(132)
Net periodic benefit cost (benefit)	55	174	(142)
Amounts recognized in other comprehensive income (pre-tax):
Current year prior service cost (credit)	0	1	(3)
Amortization of prior service (cost) credit	0	0	0
Total recognized in other comprehensive income	0	1	(3)
Total recognized in net periodic cost and other comprehensive income	$ 55	$ 175	$ (145)
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate used to measure service cost	3.60%	3.80%	1.70%
Discount rate used to measure interest cost	3.90%	4.20%	1.70%
Expected rate of return on plan assets	5.10%	5.20%	3.10%
Rate of compensation increase	2.30%	2.30%	2.00%
Other Postretirement  Benefits
Components of net periodic benefit cost:
Service cost	$ 67	$ 67	$ 99
Interest cost	131	144	80
Expected return on plan assets	(7)	(11)	(12)
Curtailments, settlements and termination benefits	0	0	0
Amortization of prior service cost (credit)	(14)	(12)	(6)
Actuarial loss (gain)	(213)	(131)	(733)
Net periodic benefit cost (benefit)	(36)	57	(572)
Amounts recognized in other comprehensive income (pre-tax):
Current year prior service cost (credit)	0	(2)	(30)
Amortization of prior service (cost) credit	14	12	6
Total recognized in other comprehensive income	14	10	(24)
Total recognized in net periodic cost and other comprehensive income	$ (22)	$ 67	$ (596)
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate used to measure service cost	5.10%	5.40%	2.80%
Discount rate used to measure interest cost	5.00%	5.30%	2.20%
Expected rate of return on plan assets	7.40%	7.40%	6.90%
Rate of compensation increase	4.00%	4.00%	4.00%