Operating Segments - Results (Details) - USD ($)	3 Months Ended
	Oct. 31, 2016	Oct. 31, 2015
Information as to operating segments
Net sales	$ 187,725,000	$ 153,779,000
Operating income	27,063,000	23,776,000
Interest expense, net	(1,093,000)	(745,000)
Income before income taxes	25,970,000	23,031,000
Operating Segment
Information as to operating segments
Operating income	35,690,000	29,319,000
General corporate
Information as to operating segments
Operating income	(8,627,000)	(5,543,000)
Endoscopy
Information as to operating segments
Net sales	93,828,000	71,642,000
Endoscopy | Operating Segment
Information as to operating segments
Operating income	17,561,000	12,459,000
Water Purification and Filtration
Information as to operating segments
Net sales	49,873,000	44,712,000
Water Purification and Filtration | Operating Segment
Information as to operating segments
Operating income	8,920,000	7,813,000
Healthcare Disposables
Information as to operating segments
Net sales	36,799,000	27,352,000
Healthcare Disposables | Operating Segment
Information as to operating segments
Operating income	7,396,000	6,360,000
Dialysis
Information as to operating segments
Net sales	7,225,000	10,073,000
Dialysis | Operating Segment
Information as to operating segments
Operating income	$ 1,813,000	$ 2,687,000