Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Inventory [Line Items]
Long-term prepaid manufacturing	$ 7,800	$ 10,900
Long-term inventories	31,608	$ 9,645
Charge for reserve on excess and obsolescence of inventories	3,820
Cost of Sales
Inventory [Line Items]
Charge for reserve on excess and obsolescence of inventories	$ 3,800

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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