Litigation and Other Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Apr. 30, 2015	Jan. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
EPA estimated remediation cost		$ 22.0
Litigation Liability	$ 1.3
Remaining litigation liability		$ 1.0

Total anticipated costs associated with remediation, site restoration, postclosure, monitoring commitments, or other exit costs that may occur on the sale, disposal, or abandonment of a particular property resulting from unanticipated contamination of the assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.Y.Q4)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

Name:	us-gaap_EnvironmentalExitCostsAnticipatedCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration