Inventories - Additional Information (Detail) $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($)
Inventory Disclosure [Abstract]
Impact on income as a result of LIFO liquidations	$ 0

The effect of liquidating LIFO (last in first out) inventory layers on income.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SAB Topic 11.F)
-URI http://asc.fasb.org/extlink&oid=27011343&loc=d3e100079-122729

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration