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Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Net periodic benefit cost |  |  | $ 163 | $ 246
Net periodic benefit costs continuing and discontinued |  |  |  |
Net periodic benefit cost |  |  | 163 | 246
Pension Benefits [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost | $ 22 | $ 43 | 67 | 124
Interest cost | 59 | 114 | 175 | 358
Expected return on plan assets | (82) | (187) | (248) | (558)
Recognized net actuarial loss | 55 | 104 | 165 | 308
Amortization of prior service cost (benefits) | 1 | 4 | 4 | 12
Settlements |  | 13 |  | 15
Special termination benefits |  |  |  | 1
Net periodic benefit cost | 55 | 91 | 163 | 260
Net periodic benefit costs continuing and discontinued |  |  |  |
Discontinued operations |  | 41 |  | 114
Net amount recognized in Statement of Consolidated Operations | 55 | 50 | 163 | 146
Net periodic benefit cost | 55 | 91 | 163 | 260
Other Postretirement Benefits [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost | 2 | 3 | 6 | 10
Interest cost | 7 | 16 | 22 | 53
Recognized net actuarial loss | 2 | 8 | 4 | 19
Amortization of prior service cost (benefits) | (2) | (6) | (6) | (19)
Net periodic benefit cost | 9 | 21 | 26 | 63
Net periodic benefit costs continuing and discontinued |  |  |  |
Discontinued operations |  | 12 |  | 37
Net amount recognized in Statement of Consolidated Operations | 9 | 9 | 26 | 26
Net periodic benefit cost | $ 9 | $ 21 | $ 26 | $ 63

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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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(5) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(7) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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