Operating Segments - Results (Details) - USD ($)
3 Months Ended 6 Months Ended
Jan. 31, 2016
Jan. 31, 2015
Jan. 31, 2016
Jan. 31, 2015
Information as to operating segments        
Net sales $ 158,271,000 $ 135,430,000 $ 312,050,000 $ 272,241,000
Operating income 24,396,000 18,301,000 48,172,000 37,348,000
Interest expense, net (871,000) (646,000) (1,616,000) (1,180,000)
Income before income taxes 23,525,000 17,655,000 46,556,000 36,168,000
Operating Segment        
Information as to operating segments        
Operating income 29,660,000 23,066,000 58,979,000 46,292,000
General corporate        
Information as to operating segments        
Operating income (5,264,000) (4,765,000) (10,807,000) (8,944,000)
Endoscopy        
Information as to operating segments        
Net sales 81,458,000 58,970,000 153,100,000 114,902,000
Endoscopy | Operating Segment        
Information as to operating segments        
Operating income 14,664,000 8,396,000 27,123,000 15,854,000
Water Purification and Filtration        
Information as to operating segments        
Net sales 43,252,000 42,356,000 87,964,000 84,724,000
Water Purification and Filtration | Operating Segment        
Information as to operating segments        
Operating income 7,589,000 8,121,000 15,402,000 15,777,000
Healthcare Disposables        
Information as to operating segments        
Net sales 26,026,000 25,197,000 53,378,000 54,534,000
Healthcare Disposables | Operating Segment        
Information as to operating segments        
Operating income 5,673,000 4,469,000 12,033,000 10,823,000
Dialysis        
Information as to operating segments        
Net sales 7,535,000 7,314,000 17,608,000 14,800,000
Dialysis | Operating Segment        
Information as to operating segments        
Operating income $ 1,734,000 1,481,000 $ 4,421,000 2,931,000
Other.        
Information as to operating segments        
Net sales   1,593,000   3,281,000
Other. | Operating Segment        
Information as to operating segments        
Operating income   $ 599,000   $ 907,000