Supplemental Cash Flow Information (Details) - USD ($)	12 Months Ended
	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Supplemental Cash Flow Information
Interest paid	$ 1,970,000	$ 1,787,000	$ 2,643,000
Income tax payments	$ 25,239,000	$ 20,481,000	$ 17,116,000