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Pensions and Other Postretirement Benefits - Schedule of Net Benefit Costs (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |
Non-service cost components of net periodic pension and OPEB income | $ 401 | $ 369 | $ 1,200 | $ 1,000
Global OPEB Plans [Member] |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |
Service cost | 5 | 4 | 15 | 14
Interest cost | 49 | 51 | 147 | 149
Expected return on plan assets | 0 | 0 | 0 | 0
Amortization of prior service cost (credit) | (4) | (3) | (11) | (10)
Amortization of net actuarial (gains) losses | 14 | 8 | 40 | 24
Curtailments, settlements and other | 0 | 0 | 0 | 0
Net periodic pension and OPEB (income) expense | 64 | 60 | 191 | 177
U.S. [Member] | Pension Plan [Member] |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |
Service cost including administrative expenses | 83 | 79 | 248 | 237
Interest cost | 513 | 536 | 1,538 | 1,608
Expected return on plan assets | (972) | (919) | (2,917) | (2,757)
Amortization of prior service cost (credit) | (1) | (1) | (3) | (3)
Amortization of net actuarial (gains) losses | 2 | (2) | 7 | (5)
Curtailments, settlements and other | 0 | 0 | 0 | 0
Net periodic pension and OPEB (income) expense | (375) | (307) | (1,127) | (920)
Non-U.S. [Member] | Pension Plan [Member] |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |
Service cost | 33 | 45 | 138 | 131
Interest cost | 112 | 115 | 349 | 366
Expected return on plan assets | (201) | (185) | (621) | (528)
Amortization of prior service cost (credit) | 1 | 2 | 3 | 4
Amortization of net actuarial (gains) losses | 35 | 29 | 109 | 124
Curtailments, settlements and other | 18 | 0 | 18 | 0
Net periodic pension and OPEB (income) expense | (2) | $ 6 | (4) | $ 97
Estimated contributions in 2018 | 1,600 |  | 1,600 |
Non-U.S. [Member] | Pension Plan [Member] | U.K. and Canada [Member] |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |
Contributions to pension plans | 584 |  |  |
Non-U.S. [Member] | Pension Plan [Member] | Korea [Member] |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |  |
Estimated contributions in 2018 | $ 300 |  | $ 300 |

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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan. + 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 (h)(4) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920 + Details
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