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Guarantees (Narrative) (Details) - USD ($)	3 Months Ended
Guarantees (Narrative) (Details) - USD ($)	Oct. 31, 2023	Oct. 31, 2022	Jul. 31, 2023
Advanced Filtration Systems, Inc.
Guarantor Obligations
Investment earnings	$ 1,700,000	$ 1,300,000
Unsecured revolving credit facility
Guarantor Obligations
Available credit facilities	63,000,000
Multi-Currency Revolving Credit Facility
Guarantor Obligations
Available credit facilities	17,000,000
Advanced Filtration Systems, Inc.
Guarantor Obligations
AFSI outstanding debt	$ 56,600,000		$ 59,600,000