Inventories (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Inventories
Parts and work-in-process	$ 122	$ 153
Finished goods	69	91
Total inventories	191	244
Inventory Write-down	$ 48	$ 9	$ 20

Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of merchandise or goods held by the company that are readily available for sale.

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- Definition

Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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- Definition

The aggregate carrying amount as of the balance sheet date of items held by the entity which are partially completed at the time of measurement and unprocessed items that will go through the production process and become part of the final product. Includes supplies used directly or indirectly in the manufacturing or production process. This element may be used when the reporting entity combines work in process and raw materials into an aggregate amount.

+ References

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- Definition

Amount of loss from reductions in inventory due to subsequent measurement adjustments, including, but not limited to, physical deterioration, obsolescence, or changes in price levels.

+ References

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