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Inventories - Additional information (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Classes Of Inventories [Line Items] |  |  |
Inventory write-downs, net of reversals |  | $ 51 | $ 192
Net inventory write- back | $ 7 |  |
Inventory write offs | 74 |  |
Disclosure - Inventories - Additional information (Detail) [Line Items] |  |  |
Inventories pledged as security for liabilities | 611 | $ 564 |
Previously Stated [Member] |  |  |
Classes Of Inventories [Line Items] |  |  |
Net inventory write- back | $ 81 |  |

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