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Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Parenthetical) (Detail) - Other Income [Member] - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
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Sep. 30, 2016 | Sep. 30, 2016
Energy Contracts [Member] |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Net amount reclassified to earnings | $ 50 | $ 50
Interest Rate Contracts [Member] |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Net amount reclassified to earnings |  | 7
Nickel Contracts [Member] |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Net amount reclassified to earnings | $ 50 | $ 50

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Amount before tax of reclassification adjustment from accumulated other comprehensive (income) loss related to net period benefit cost (credit) for pension and other postretirement defined benefit plans. + References No definition available. + Details
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