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Components of Accumulated Other Comprehensive Income, Net of Tax (Detail) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2018 | Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Beginning Balance, income taxes |  | $ (39) | $ 26 |
Changes in value, income taxes |  | (6) | 10 |
Amounts reclassified to earnings, income taxes |  | (3) | (6) |
Amounts reclassified to retained earnings, income taxes | [1] | 0 |  |
Net change, income taxes |  | (9) | 4 |
Ending Balance, income taxes |  | (48) | 30 |
Beginning Balance, net of tax | [2] | 8,734 |  |
Changes in value, net of tax |  | 13 | (16) |
Amounts reclassified to earnings, net of tax |  | 13 |  |
Amounts reclassified to retained earnings, net of tax | [1] | 7 |  |
Total other comprehensive income (loss), net |  | 33 | (7) | [3]
Ending Balance, net of tax |  | 8,336 |  |
Accumulated Other Comprehensive Income (Loss) |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Beginning Balance, net of tax |  | (1,147) | (829) |
Amounts reclassified to earnings, net of tax |  |  | 9 |
Ending Balance, net of tax |  | (1,114) | (836) |
Pension and Other Postretirement Liabilities |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Beginning Balance, before tax |  | (1,102) | (854) |
Changes in value, before tax |  | 23 | (26) |
Amounts reclassified to earnings, before tax |  | 16 | 13 |
Net change, before tax |  | 39 | (13) |
Ending Balance, before tax |  | (1,063) | (867) |
Investments and Other |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Beginning Balance, before tax |  | (6) | (1) |
Changes in value, before tax |  | (4) |  |
Amounts reclassified to earnings, before tax |  |  | 2 |
Amounts reclassified to retained earnings, before tax | [1] | 7 |  |
Net change, before tax |  | 3 | 2 |
Ending Balance, before tax |  | $ (3) | $ 1 |
[1] | This amount represents the unrealized loss on the Company's investment in Azul, S.A. ("Azul") which was previously classified as an available-for-sale security.
[2] | Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements contained in Part I, Item 1 of this report for additional information.
[3] | Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) and Accounting Standards Update No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. See Note 1 to the financial statements contained in Part I, Item 1 of this report for additional information.

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- Definition Reclassification from accumulated other comprehensive income, to retained earnings current period, net of tax. + References No definition available. + Details
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- Definition Amount before tax of increase (decrease) in accumulated equity from transactions and other events and circumstances from non-owner sources, attributable to parent. Excludes net income (loss), and accumulated changes in equity from transactions resulting from investments by owners (distributions to owners). + References No definition available. + Details
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