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Guarantees (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
Guarantees (Narrative) (Details) - USD ($)	Jan. 31, 2024	Jan. 31, 2023	Jan. 31, 2024	Jan. 31, 2023	Jul. 31, 2023
Advanced Filtration Systems, Inc.
Guarantor Obligations
Investment earnings	$ 2,500,000	$ 500,000	$ 4,200,000	$ 1,800,000
Unsecured revolving credit facility
Guarantor Obligations
Available credit facilities	63,000,000		63,000,000
Multi-Currency Revolving Credit Facility
Guarantor Obligations
Available credit facilities	17,000,000		17,000,000
Advanced Filtration Systems, Inc.
Guarantor Obligations
AFSI outstanding debt	$ 55,400,000		$ 55,400,000		$ 59,600,000