Summary of Significant Accounting Policies - Revenue (Details) $ in Thousands	12 Months Ended
Jul. 31, 2017 USD ($) customer	Jul. 31, 2016 USD ($)	Jul. 31, 2015 USD ($)
Revenue recognition - reductions
Number of customers with products shipped FOB destination \| customer	1
Volume rebates \| $	$ 6,291	$ 5,944	$ 5,597

The aggregate selling price reductions recognized during an accounting period including, but not limited to, the sale of defective or nonconforming goods, a strategy to increase sales (generally over the short-term), move slow-moving items, develop distribution channels, or reward valuable customers. Allowances are a deduction from gross revenue in arriving at net revenue.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(a))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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