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Postretirement benefits Schedule of Allocation of Plan Assets (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | $ 4,291 | $ 3,016
Available for sale, Fair Value | 85,488 | 78,470
Other Investments | 6,062 | 5,277
Fair Value, Recurring [Member] | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 2,803 | 1,575
Available for sale, Fair Value | 2,664 | 3,400
Equity Securities |  | 713
Other Investments | 412 | 381
Fair Value, Recurring [Member] | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 1,482 | 1,440
Available for sale, Fair Value | 80,864 | 73,365
Equity Securities |  | 0
Other Investments | 377 | 303
Fair Value, Recurring [Member] | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 6 | 1
Available for sale, Fair Value | 1,960 | 1,705
Equity Securities |  | 57
Other Investments | 10 | 11
Other Investments [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Other Investments | 95 | 95
Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Other Investments | 4,921 | 4,244
UNITED STATES | Pension Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 55 | 84
Equity Securities | 1,467 | 1,050
Defined benefit plan, fair value of plan assets excluding measured using NAV | 2,873 | 2,290
UNITED STATES | Pension Plan [Member] | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 18 | 10
Equity Securities | 1,467 | 1,050
Defined benefit plan, fair value of plan assets excluding measured using NAV | 1,951 | 1,493
UNITED STATES | Pension Plan [Member] | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 37 | 74
Equity Securities | 0 | 0
Defined benefit plan, fair value of plan assets excluding measured using NAV | 922 | 797
UNITED STATES | Pension Plan [Member] | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 0 | 0
Available for sale, Fair Value | 0 |
Equity Securities | 0 | 0
Defined benefit plan, fair value of plan assets excluding measured using NAV | 0 | 0
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 600 | 515
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member] | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 466 | 433
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member] | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 134 | 82
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member] | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value |  | 0
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 749 | 641
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 0 | 0
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 749 | 641
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value |  | 0
UNITED STATES | Other Investments [Member] | Pension Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Other Investments | 428 | 494
Non - U.S. | Pension Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 2 | 7
Equity Securities | 430 | 474
Defined benefit plan, fair value of plan assets excluding measured using NAV | 1,030 | 899
Non - U.S. | Pension Plan [Member] | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 2 | 7
Equity Securities | 112 | 103
Defined benefit plan, fair value of plan assets excluding measured using NAV | 114 | 110
Non - U.S. | Pension Plan [Member] | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 0 | 0
Equity Securities | 318 | 371
Defined benefit plan, fair value of plan assets excluding measured using NAV | 916 | 789
Non - U.S. | Pension Plan [Member] | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 0 | 0
Equity Securities | 0 | 0
Defined benefit plan, fair value of plan assets excluding measured using NAV | 0 | 0
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 598 | 418
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 0 | 0
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 598 | 418
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 0 | 0
Non - U.S. | Other Investments [Member] | Pension Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Other Investments | 107 | 109
Non - U.S. | Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value [Member] | Pension Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Other Investments | 4 |
States, municipalities, and political subdivisions |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 7,515 | 10,786
States, municipalities, and political subdivisions | Fair Value, Recurring [Member] | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 0 | 0
States, municipalities, and political subdivisions | Fair Value, Recurring [Member] | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 7,515 | 10,786
States, municipalities, and political subdivisions | Fair Value, Recurring [Member] | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 0 | $ 0
States, municipalities, and political subdivisions | UNITED STATES | Pension Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 2 |
States, municipalities, and political subdivisions | UNITED STATES | Pension Plan [Member] | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | $ 2 |

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