Supplementary Balance Sheet Information (Components Of Accounts Payable And Accrued Liabilities) (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Jul. 31, 2017	Apr. 30, 2017
Balance Sheet Related Disclosures [Abstract]
Trade payables	$ 58,228	$ 71,558	$ 51,305
Deferred revenue	251,110	240,096	206,534
Accrued salaries, wages and deferred compensation	24,645	44,869	36,162
Accrued benefits	37,776	32,505	36,401
Deposits	24,326	23,742	22,117
Other liabilities	33,773	54,899	50,766
Total accounts payable and accrued liabilities	$ 429,858	$ 467,669	$ 403,285