Supplementary Balance Sheet Information (Components Of Accounts Payable And Accrued Liabilities) (Details) - USD ($) $ in Thousands	Apr. 30, 2020	Jul. 31, 2019	Apr. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Trade payables	$ 62,101	$ 96,377	$ 80,218
Deferred revenue	219,395	335,669	297,874
Accrued salaries, wages and deferred compensation	16,184	50,318	37,817
Accrued benefits	44,536	37,797	42,732
Deposits	27,053	32,108	32,090
Other liabilities	80,005	55,588	52,329
Total accounts payable and accrued liabilities	$ 449,274	$ 607,857	$ 543,060