Restructuring Charges (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016	Jul. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0	$ 1,000,000	$ 0	$ 8,500,000
Restructuring reserve	0		$ 0		$ 0
Cost of Sales
Restructuring Cost and Reserve [Line Items]
Restructuring charges		900,000		4,100,000
Operating Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges		100,000		4,400,000
Engine Products
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1,000,000			$ 6,000,000
Industrial Filtration Solutions Products
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 2,500,000