Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2020	Jan. 31, 2019	Jul. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 2,300	$ 2,600	$ 4,800	$ 5,500
Amortized intangibles:
Accumulated amortization	(29,912)		(29,912)		$ (25,142)
Net intangibles	50,291		50,291		55,156
Supply contracts and customer relationships
Amortized intangibles:
Gross carrying amount	49,006		49,006		49,109
Trade names
Amortized intangibles:
Gross carrying amount	23,506		23,506		23,501
Licenses and databases
Amortized intangibles:
Gross carrying amount	$ 7,691		$ 7,691		$ 7,688