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Acquisitions (Details Textuals) $ in Thousands	12 Months Ended
Acquisitions (Details Textuals) $ in Thousands	Jul. 31, 2015 USD ($)	Jul. 31, 2014 USD ($) business	Jul. 31, 2013 USD ($) business
Business Acquisition [Line Items]
Goodwill	$ 271,850	$ 283,780	$ 267,463
Intangibles, net	$ 17,857	$ 25,242
Covenants not to compete
Business Acquisition [Line Items]
Useful life of intangible assets	3 years	4 years
Intangibles, net	$ 791	$ 1,182
Licenses and databases
Business Acquisition [Line Items]
Useful life of intangible assets	2 years	3 years
Intangibles, net	$ 449	$ 367
2014 Acquisitions
Business Acquisition [Line Items]
Total purchase price		$ 14,500
Increase (decrease) in goodwill during the period	(800)
Increase in intangible assets	$ 900
2014 Acquisitions \| Covenants not to compete \| Minimum
Business Acquisition [Line Items]
Useful life of intangible assets		3 years
2014 Acquisitions \| Covenants not to compete \| Maximum
Business Acquisition [Line Items]
Useful life of intangible assets		8 years
2014 Acquisitions \| Supply contracts \| Minimum
Business Acquisition [Line Items]
Useful life of intangible assets		3 years
2014 Acquisitions \| Supply contracts \| Maximum
Business Acquisition [Line Items]
Useful life of intangible assets		8 years
2014 Acquisitions \| Customer relationships \| Minimum
Business Acquisition [Line Items]
Useful life of intangible assets		3 years
2014 Acquisitions \| Customer relationships \| Maximum
Business Acquisition [Line Items]
Useful life of intangible assets		8 years
2014 Acquisitions \| Trade name \| Minimum
Business Acquisition [Line Items]
Useful life of intangible assets		3 years
2014 Acquisitions \| Trade name \| Maximum
Business Acquisition [Line Items]
Useful life of intangible assets		8 years
2014 Acquisitions \| Licenses and databases \| Minimum
Business Acquisition [Line Items]
Useful life of intangible assets		3 years
2014 Acquisitions \| Licenses and databases \| Maximum
Business Acquisition [Line Items]
Useful life of intangible assets		8 years
2013 Acquisitions
Business Acquisition [Line Items]
Total purchase price			$ 86,958
Increase (decrease) in goodwill during the period		$ (800)
Voting stock, percent			100.00%
Accrued liabilities		11,500
Intangibles, net		9,300
Pre-acquisition contingency low		7,000
Pre-acquisition contingency high		28,000
Fair value of this contingency		$ 14,000
CA
Business Acquisition [Line Items]
Number of businesses acquired \| business		1
DE and ES
Business Acquisition [Line Items]
Number of businesses acquired \| business			2