Operating Segments (Details 2) - USD ($)	3 Months Ended
	Oct. 31, 2015	Oct. 31, 2014	Jul. 31, 2015
Information as to operating segments
Net sales	$ 153,779,000	$ 136,811,000
Operating income	23,776,000	19,047,000
Interest expense, net	(745,000)	(534,000)
Income before income taxes	23,031,000	18,513,000
Identifiable assets	677,662,000		$ 584,031,000
Capital expenditures	3,167,000	3,055,000
Operating Segment
Information as to operating segments
Operating income	29,319,000	23,226,000
General corporate
Information as to operating segments
Operating income	(5,543,000)	(4,179,000)
Endoscopy
Information as to operating segments
Net sales	71,642,000	55,932,000
Endoscopy | Operating Segment
Information as to operating segments
Operating income	12,459,000	7,458,000
Water Purification and Filtration
Information as to operating segments
Net sales	44,712,000	42,368,000
Water Purification and Filtration | Operating Segment
Information as to operating segments
Operating income	7,813,000	7,656,000
Healthcare Disposables
Information as to operating segments
Net sales	27,352,000	29,337,000
Healthcare Disposables | Operating Segment
Information as to operating segments
Operating income	6,360,000	6,354,000
Dialysis
Information as to operating segments
Net sales	10,073,000	7,486,000
Dialysis | Operating Segment
Information as to operating segments
Operating income	$ 2,687,000	1,450,000
Other.
Information as to operating segments
Net sales		1,688,000
Other. | Operating Segment
Information as to operating segments
Operating income		$ 308,000