Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Inventory [Line Items]
Long-term inventories	$ 33,296		$ 9,645
Long-term prepaid manufacturing	9,100		$ 10,900
Charge for reserve on excess and obsolescence of inventories	4,131	$ 2,246
Cost of Sales
Inventory [Line Items]
Charge for reserve on excess and obsolescence of inventories	$ 4,100

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.

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