Intangibles, Net (Details) (USD $)	12 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2009
Amortized intangible assets:
Gross Carrying Amount	$ 39,471,000	$ 34,379,000
Accumulated Amortization	(26,723,000)	(21,363,000)
Net Book Value	12,748,000	13,016,000
Amortization Expenses	4,700,000	3,900,000	4,100,000
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
2012		4,926,000
2013		4,124,000
2014		1,338,000
2015		1,090,000
2016		875,000
Thereafter		395,000
Total		12,748,000
Covenants Not To Compete
Amortized intangible assets:
Gross Carrying Amount	10,896,000	10,697,000
Accumulated Amortization	(10,486,000)	(10,233,000)
Net Book Value	410,000	464,000
Weighted Average Remaining Useful Life (in years)	3	1
Supply Contracts
Amortized intangible assets:
Gross Carrying Amount	27,238,000	22,365,000
Accumulated Amortization	(15,409,000)	(10,521,000)
Net Book Value	11,829,000	11,844,000
Weighted Average Remaining Useful Life (in years)	3	4
Licenses and Databases
Amortized intangible assets:
Gross Carrying Amount	1,337,000	1,317,000
Accumulated Amortization	(828,000)	(609,000)
Net Book Value	$ 509,000	$ 708,000
Weighted Average Remaining Useful Life (in years)	3	4