Actuarial Assumptions (Detail)	12 Months Ended
Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Discount rate	3.50%	4.00%	4.20%
Expected return on assets	6.20%	6.00%	6.00%

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration