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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

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- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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