Leases - Supplemental income statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018
Operating lease costs
Amortization of right-of-use assets	$ 10,292
Interest on lease obligations	1,226
Finance lease costs:
Amortization of right-of-use assets	650
Interest on lease obligations	885
Variable lease costs	3,256
Short-term lease costs	1,427
Net lease cost	$ 17,736
Rental expense		$ 9,601	$ 8,801