Postemployment benefit plans (Details B) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Other changes in plan assets and benefit obligations recognized in other comprehensive income (pre-tax):
Current year prior service cost (credit)	$ 0	$ (1)	$ (4)
Amortization of prior service (cost) credit	40	38	40
U.S. pensions
Components of net periodic benefit cost:
Service cost	0	0	115
Interest cost	330	483	600
Expected return on plan assets	(718)	(791)	(721)
Curtailments, settlements and termination benefits	0	(1)	(1)
Amortization of prior service cost / (credit)	0	0	0
Actuarial loss / (gain)	(487)	162	72
Net periodic benefit cost (benefit)	(875)	(147)	65
Other changes in plan assets and benefit obligations 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	$ (875)	$ (147)	$ 65
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate used to measure service cost	0.00%	0.00%	4.30%
Discount rate used to measure interest cost	1.80%	2.80%	3.90%
Expected rate of return on plan assets	4.20%	5.10%	5.90%
Rate of compensation increase	0.00%	0.00%	4.00%
Expected return on plan assets, next fiscal year (as a percent)	4.00%
Additional percentage amount added to long-term passive rate of returns to arrive at the long-term expected rate of return (as a percent)	0.35%	0.40%	0.40%
Non-U.S. pensions
Components of net periodic benefit cost:
Service cost	$ 57	$ 55	$ 80
Interest cost	53	68	94
Expected return on plan assets	(128)	(135)	(148)
Curtailments, settlements and termination benefits	(1)	30	(7)
Amortization of prior service cost / (credit)	0	0	0
Actuarial loss / (gain)	(115)	32	90
Net periodic benefit cost (benefit)	(134)	50	109
Other changes in plan assets and benefit obligations recognized in other comprehensive income (pre-tax):
Current year prior service cost (credit)	0	8	(4)
Amortization of prior service (cost) credit	0	0	0
Total recognized in other comprehensive income	0	8	(4)
Total recognized in net periodic cost and other comprehensive income	$ (134)	$ 58	$ 105
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate used to measure service cost	1.40%	1.50%	2.50%
Discount rate used to measure interest cost	1.20%	1.70%	2.30%
Expected rate of return on plan assets	2.90%	3.30%	3.80%
Rate of compensation increase	2.00%	2.00%	3.00%
Expected return on plan assets, next fiscal year (as a percent)	3.10%
Other postretirement benefits
Components of net periodic benefit cost:
Service cost	$ 100	$ 94	$ 80
Interest cost	64	103	136
Expected return on plan assets	(6)	(12)	(18)
Curtailments, settlements and termination benefits	0	0	0
Amortization of prior service cost / (credit)	(40)	(38)	(40)
Actuarial loss / (gain)	(231)	189	306
Net periodic benefit cost (benefit)	(113)	336	464
Other changes in plan assets and benefit obligations recognized in other comprehensive income (pre-tax):
Current year prior service cost (credit)	0	(7)	8
Amortization of prior service (cost) credit	40	38	40
Total recognized in other comprehensive income	40	31	48
Total recognized in net periodic cost and other comprehensive income	$ (73)	$ 367	$ 512
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate used to measure service cost	2.50%	3.20%	4.10%
Discount rate used to measure interest cost	1.60%	2.80%	3.90%
Expected rate of return on plan assets	6.50%	7.00%	7.20%
Rate of compensation increase	4.00%	4.00%	4.10%
Assumed increase in health care trend rate
Assumed increase in health care trend rate over the current period to calculate benefit expenses (as a percent)	5.80%
Assumed increase in health care trend rate for the next year to calculate benefit expenses (as a percent)	5.60%
Year that heath care trend rate is assumed to reach ultimate trend rate (year)	2025
Ultimate health care cost trend rate (as a percent)	5.00%
General inflation rate that forms a part of ultimate health care trend rate (as a percent)	3.00%
Additional healthcare inflation rate that forms a part of ultimate health care trend rate (as a percent)	2.00%