Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015	Jul. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 1,500	$ 1,700	$ 3,000	$ 3,600
Amortized intangibles:
Accumulated amortization	(21,281)		(21,281)		$ (18,967)
Net intangibles	14,408		14,408		17,857
Covenants not to compete
Amortized intangibles:
Gross carrying amount	1,663		1,663		1,691
Supply contracts & customer relationships
Amortized intangibles:
Gross carrying amount	26,459		26,459		27,506
Trade name
Amortized intangibles:
Gross carrying amount	5,097		5,097		5,129
Licenses and databases
Amortized intangibles:
Gross carrying amount	$ 2,470		$ 2,470		$ 2,498