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Pensions And Other Postretirement Benefits Contributions and Plan Amendments (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Defined Contribution Plan [Abstract] |  |  |  |
Employer contributions to defined contribution plans |  | $ 650 | $ 589 | $ 530
US Pension and OPEB Plans [Member] | U.S. [Member] |  |  |  |
Defined Contribution Plan [Abstract] |  |  |  |
Remeasurement decrease due to mortality assumptions | $ 888 |  |  |
Pension Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Years of service |  | 30 years |  |
Employer contributions |  | $ 1,230 | 3,076 | 1,203
Pension Plan [Member] | U.S. [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer contributions |  | 77 | 2,054 |
Pension Plan [Member] | U.S. [Member] | Nonqualified Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Estimated contributions in next fiscal year |  | $ 70 |  |
Pension Plan [Member] | U.S. [Member] | Qualified Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Period of time for which there are no mandatory contributions for qualified plans |  | 5 years |  |
Mandatory contributions over the next five years |  | $ 0 |  |
Pension Plan [Member] | U.S. [Member] | U.S. Hourly [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer contributions |  |  | 2,000 |
Pension Plan [Member] | U.S. [Member] | U.S. Hourly and Salaried [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer contributions |  | 77 | 2,054 | 95
Pension Plan [Member] | Non-U.S. [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer contributions |  | 1,153 | 1,022 | 1,108
Estimated contributions in next fiscal year |  | 900 |  |
Pension Plan [Member] | Canada and United Kingdom [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Mandatory contributions over the next five years |  | 1,200 |  |
Other Postretirement Benefits Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer contributions |  | 406 | 378 |
Other Postretirement Benefits Plan [Member] | U.S. [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer contributions |  | $ 323 | $ 335 | $ 340

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- Definition For U.S. and Canadian hourly employees hired prior to specified dates, represents the required number of years of service, before normal retirement age, to be eligible for supplemental benefits. + References No definition available. + Details
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