Schedule of Changes In Product Warranty Reserves (Detail) (USD $)	3 Months Ended	9 Months Ended
Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2013	Apr. 30, 2012
Product Warranty
Beginning balance	$ 79,210	$ 62,020	$ 73,280	$ 66,054
Provision	24,479	20,751	69,829	50,284
Payments	(19,652)	(15,333)	(59,072)	(48,900)
Ending balance	$ 84,037	$ 67,438	$ 84,037	$ 67,438

Represents the aggregate decrease in the liability for payments made (in cash or in kind) to satisfy claims under the terms of the standard product warranty. Does not include any Increase or Decrease in the liability for payments related to extended product warranties.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 45

-Paragraph 14

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph ((c)(2))

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

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