Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Inventory [Line Items]
Long-term inventories	$ 23,805	$ 9,645
Charge for reserve on excess and obsolescence of inventories	3,945
Reserve for excess and obsolescence of inventories	6,600
Long-term prepaid manufacturing	7,800	$ 10,900
Cost of Sales
Inventory [Line Items]
Charge for reserve on excess and obsolescence of inventories	$ 3,900

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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