Subsidiary Guarantors - Additional Information (Detail) (Guarantors [Member])	Jul. 31, 2013
Guarantors [Member]
Condensed Financial Statements, Captions [Line Items]
Ownership percentage by parent	100.00%

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

No definition available.

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