Inventory - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Inventory includes write-downs for excess and obsolete inventory	$ 1.1	$ 1.1

Amount of valuation reserve for inventory.

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Name:	us-gaap_InventoryValuationReserves
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant