Guarantees (Details) - USD ($)	3 Months Ended		9 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018	Jul. 31, 2018
Guarantor Obligations [Line Items]
Net sales	$ 712,800,000	$ 700,000,000	$ 2,117,900,000	$ 2,009,500,000
Contingent liability for standby letters of credit, issued and outstanding	11,200,000		11,200,000		$ 8,200,000
Amount drawn upon letters of credit	0		0		$ 0
Advanced Filtration Systems, Inc.
Guarantor Obligations [Line Items]
Outstanding debt of joint venture	38,200,000		38,200,000
Advanced Filtration Systems, Inc.
Guarantor Obligations [Line Items]
Joint venture investment earnings (loss)	400,000	600,000	100,000	1,100,000
Advanced Filtration Systems, Inc. | Royalty
Guarantor Obligations [Line Items]
Net sales	$ 1,500,000	$ 1,700,000	$ 4,800,000	$ 5,300,000