Guarantees (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018
Guarantor Obligations
Contingent liability for standby letters of credit	$ 7.5	$ 11.0
Amounts drawn for letters of credit	0.0	0.0
Investment in earnings	5.2	2.2	$ 3.6
Advanced Filtration Systems Inc.
Guarantor Obligations
AFSI outstanding debt (the Company guarantees half)	40.0	38.8
Investment in earnings	2.2	(0.3)	1.3
Advanced Filtration Systems Inc. | Royalty
Guarantor Obligations
Royalty income	$ 6.8	$ 6.5	$ 7.0