Fair Value Measurement of Assets and Liabilities - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
Apr. 30, 2015	Jul. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefit plans assets percentage invested in bank-managed portfolios	100.00%
Transfers between Levels 1, 2 or 3	$ 0	$ 0

Plan assets of a defined benefit plan, as a percentage of projected benefit obligation.

No definition available.

Name:	us-gaap_DefinedBenefitPlanFundedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant