Postemployment benefit plans - Schedule of changes in projected benefit obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Change in benefit obligation:
Actuarial loss (gain)	$ (154)	$ (97)	$ (606)
Pension Plan | U.S. Pension Benefits
Defined Benefit Plan Disclosure
Accumulated benefit obligation, end of year	12,171	13,137
Change in benefit obligation:
Benefit obligation, beginning of year	13,137	13,069
Service cost	0	0	0
Interest cost	625	656	401
Plan amendments	0	0
Actuarial loss (gain)	(603)	394
Foreign currency exchange rates	0	0
Participant contributions	0	0
Benefits paid - gross	(988)	(982)
Less: federal subsidy on benefits paid	0	0
Curtailments, settlements and termination benefits	0	0
Acquisitions, divestitures and other	0	0
Benefit obligation, end of year	12,171	13,137	13,069
Change in plan assets:
Fair value of plan assets, beginning of year	12,738	12,456
Actual return on plan assets	96	1,220
Foreign currency exchange rates	0	0
Company contributions	52	44
Participant contributions	0	0
Benefits paid	(988)	(982)
Settlements and termination benefits	0	0
Fair value of plan assets, ending of year	11,898	12,738	12,456
Over (under) funded status	(273)	(399)
Amounts recognized in Statement 3:
Other assets (non-current asset)	354	354
Accrued wages, salaries and employee benefits (current liability)	(50)	(52)
Liability for postemployment benefits (non-current liability)	(577)	(701)
Net (liability) asset recognized	(273)	(399)
Amounts recognized in AOCI (pre-tax):
Prior service cost (credit)	$ 0	$ 0
Weighted-average assumptions used to determine benefit obligation, end of year:
Discount rate	5.60%	5.00%
Rate of compensation increase	0.00%	0.00%
Pension Plan | Non-U.S.  Pension Benefits
Defined Benefit Plan Disclosure
Accumulated benefit obligation, end of year	$ 2,880	$ 3,151
Change in benefit obligation:
Benefit obligation, beginning of year	3,265	2,956
Service cost	43	40	50
Interest cost	118	124	69
Plan amendments	0	0
Actuarial loss (gain)	(31)	169
Foreign currency exchange rates	(203)	178
Participant contributions	5	5
Benefits paid - gross	(193)	(196)
Less: federal subsidy on benefits paid	0	0
Curtailments, settlements and termination benefits	(15)	(2)
Acquisitions, divestitures and other	0	(9)
Benefit obligation, end of year	2,989	3,265	2,956
Change in plan assets:
Fair value of plan assets, beginning of year	3,467	3,244
Actual return on plan assets	74	160
Foreign currency exchange rates	(194)	190
Company contributions	59	66
Participant contributions	5	5
Benefits paid	(193)	(196)
Settlements and termination benefits	(15)	(2)
Fair value of plan assets, ending of year	3,203	3,467	3,244
Over (under) funded status	214	202
Amounts recognized in Statement 3:
Other assets (non-current asset)	541	563
Accrued wages, salaries and employee benefits (current liability)	(21)	(20)
Liability for postemployment benefits (non-current liability)	(306)	(341)
Net (liability) asset recognized	214	202
Amounts recognized in AOCI (pre-tax):
Prior service cost (credit)	$ 21	$ 21
Weighted-average assumptions used to determine benefit obligation, end of year:
Discount rate	4.10%	3.90%
Rate of compensation increase	2.20%	2.30%
Other Postretirement  Benefits
Change in benefit obligation:
Benefit obligation, beginning of year	$ 2,741	$ 2,866
Service cost	67	67	99
Interest cost	131	144	80
Plan amendments	0	0
Actuarial loss (gain)	(202)	(115)
Foreign currency exchange rates	(33)	14
Participant contributions	45	43
Benefits paid - gross	(286)	(285)
Less: federal subsidy on benefits paid	6	7
Curtailments, settlements and termination benefits	0	0
Acquisitions, divestitures and other	0	0
Benefit obligation, end of year	2,469	2,741	2,866
Change in plan assets:
Fair value of plan assets, beginning of year	144	102
Actual return on plan assets	25	33
Foreign currency exchange rates	0	0
Company contributions	160	251
Participant contributions	45	43
Benefits paid	(286)	(285)
Settlements and termination benefits	0	0
Fair value of plan assets, ending of year	88	144	$ 102
Over (under) funded status	(2,381)	(2,597)
Amounts recognized in Statement 3:
Other assets (non-current asset)	0	0
Accrued wages, salaries and employee benefits (current liability)	(204)	(162)
Liability for postemployment benefits (non-current liability)	(2,177)	(2,435)
Net (liability) asset recognized	(2,381)	(2,597)
Amounts recognized in AOCI (pre-tax):
Prior service cost (credit)	$ (5)	$ (19)
Weighted-average assumptions used to determine benefit obligation, end of year:
Discount rate	5.60%	5.10%
Rate of compensation increase	4.00%	4.00%