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Postretirement benefits Schedule of Allocation of Plan Assets (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | $ 3,016 | $ 3,561
Available for sale, Fair Value | 78,470 | 78,939
Equity Securities |  | 937
Other Investments | 5,277 | 4,672
Pension Plan [Member] | UNITED STATES |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 84 | 61
Equity Securities | 1,050 | 1,154
Defined benefit plan, fair value of plan assets excluding measured using NAV | 2,290 | 2,432
Pension Plan [Member] | UNITED STATES | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 10 | 9
Equity Securities | 1,050 | 1,154
Defined benefit plan, fair value of plan assets excluding measured using NAV | 1,493 | 1,609
Pension Plan [Member] | UNITED STATES | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 74 | 52
Equity Securities | 0 | 0
Defined benefit plan, fair value of plan assets excluding measured using NAV | 797 | 823
Pension Plan [Member] | UNITED STATES | 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
Pension Plan [Member] | Non-US [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 7 | 5
Equity Securities | 474 | 614
Defined benefit plan, fair value of plan assets excluding measured using NAV | 899 | 1,075
Pension Plan [Member] | Non-US [Member] | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 7 | 5
Equity Securities | 103 | 122
Defined benefit plan, fair value of plan assets excluding measured using NAV | 110 | 127
Pension Plan [Member] | Non-US [Member] | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Short-term investments | 0 | 0
Equity Securities | 371 | 492
Defined benefit plan, fair value of plan assets excluding measured using NAV | 789 | 948
Pension Plan [Member] | Non-US [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
Pension Plan [Member] | US Treasury and Government [Member] | UNITED STATES |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 515 | 525
Pension Plan [Member] | US Treasury and Government [Member] | UNITED STATES | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 433 | 446
Pension Plan [Member] | US Treasury and Government [Member] | UNITED STATES | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 82 | 79
Pension Plan [Member] | US Treasury and Government [Member] | UNITED STATES | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 0 | 0
Pension Plan [Member] | Debt Security, Government, Non-US [Member] | UNITED STATES |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 641 | 692
Pension Plan [Member] | Debt Security, Government, Non-US [Member] | UNITED STATES | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 0 | 0
Pension Plan [Member] | Debt Security, Government, Non-US [Member] | UNITED STATES | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 641 | 692
Pension Plan [Member] | Debt Security, Government, Non-US [Member] | UNITED STATES | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 0 | 0
Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Non-US [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 418 | 456
Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Non-US [Member] | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 0 | 0
Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Non-US [Member] | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 418 | 456
Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Non-US [Member] | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Available for sale, Fair Value | 0 | 0
Other Investments [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Other Investments | 95 | 15
Other Investments [Member] | Pension Plan [Member] | UNITED STATES |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Other Investments | 494 | 677
Other Investments [Member] | Pension Plan [Member] | Non-US [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Other Investments | $ 109 | $ 95

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