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Details about Accumulated Other Comprehensive Income Components (Detail) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2018 | Mar. 31, 2017
Miscellaneous, Net |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Amortization of unrecognized losses and prior service cost | [1] | $ 16 | $ 13
Fuel Oil Contract | Aircraft Fuel |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Reclassifications of losses into earnings related to fuel derivative contracts |  |  | $ 2
[1] | This AOCI component is included in the computation of net periodic pension and other postretirement costs (see Note 5 to the financial statements included in this Part I, Item 1 for additional information).

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