Nature of Operations and Accounting Policies - Additional Information (Detail) $ in Thousands	3 Months Ended	6 Months Ended
Jan. 31, 2017 USD ($)	Jan. 31, 2017 USD ($) Segment
Accounting Policies [Abstract]
Number of reportable segments \| Segment		2
New accounting pronouncement or change in accounting principle, effect of change on net income \| $	$ 0	$ 1,843

Amount of the effect of a change in accounting principle on net income.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22583-107794

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22499-107794

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22580-107794

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