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Inventories - Additional information (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017
Classes Of Inventories [Line Items] |  |
Inventory write-downs, net of reversals | $ 48 |
Net inventory write- back |  | $ 7
Inventory partly write offs |  | 74
Disclosure - Inventories - Additional information (Detail) [Line Items] |  |
Inventories pledged as security for liabilities | $ 566 | 611
Previously Stated [Member] |  |
Classes Of Inventories [Line Items] |  |
Net inventory write- back |  | $ 81

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