Inventories - Additional Information (Detail) - USD ($)	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Inventory Disclosure [Abstract]
LIFO inventory liquidations	$ 0	$ 0
Raw materials	$ 2,200,000		$ 2,200,000

The amount of FIFO (first in first out) inventory present at the reporting date when inventory is also valued using different valuation methods.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766

Name:	us-gaap_FIFOInventoryAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant