Postretirement benefits (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
	Oct. 31, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Expenses recognized during period under the defined contributions plans		$ 211	$ 171	$ 171
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation		5,100	4,600
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		20
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		120	152	143
Actuarial Loss (gain)		1	3
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation		23	25
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		1
Defined Benefit Plan, Plan Amendment [Abstract]
(Increase) decrease in other comprehensive income, curtailment		0	0	3
Amortization of Prior Service Cost (Credit)		$ 83	84	85
Defined Benefit Plan, Equity Securities [Member] | Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage		55.00%
Defined Benefit Plan, Equity Securities [Member] | Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage		65.00%
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		$ 3,739	3,301	2,784
Actuarial Loss (gain)		441	443
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation		3,967	3,569
Defined Benefit Plan, Plan Amendment [Abstract]
(Increase) decrease in other comprehensive income, curtailment		0	0	0
Amortization of Prior Service Cost (Credit)		0	0	0
UNITED STATES | Postretirement Health Coverage [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Effect of Plan Amendment on Accumulated Benefit Obligation	$ 383
Amortization of Prior Service Cost (Credit)		79	79	80
Remaining Balance of Change in Benefit Obligation For Plan Amendment		26
UNITED STATES | Postretirement Health Coverage [Member] | Subject to Amortization [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Effect of Plan Amendment on Accumulated Benefit Obligation	$ 410
Non - U.S. | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		1,284	1,141	1,008
Actuarial Loss (gain)		135	124
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation		593	173
Defined Benefit Plan, Plan Amendment [Abstract]
(Increase) decrease in other comprehensive income, curtailment		(1)	(3)	0
Amortization of Prior Service Cost (Credit)		$ 0	$ 0	$ 0