Operating Segments - Results (Details) - USD ($)	3 Months Ended		9 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015
Information as to operating segments
Net sales	$ 173,703,000	$ 141,508,000	$ 485,753,000	$ 413,749,000
Operating income	23,263,000	21,281,000	71,435,000	58,629,000
Interest expense, net	(871,000)	(619,000)	(2,487,000)	(1,799,000)
Other expense		(2,206,000)		(2,206,000)
Income before income taxes	22,392,000	18,456,000	68,948,000	54,624,000
Operating Segment
Information as to operating segments
Operating income	31,170,000	25,781,000	90,149,000	72,073,000
General corporate
Information as to operating segments
Operating income	(7,907,000)	(4,500,000)	(18,714,000)	(13,444,000)
Endoscopy
Information as to operating segments
Net sales	91,892,000	63,734,000	244,992,000	178,636,000
Endoscopy | Operating Segment
Information as to operating segments
Operating income	16,279,000	12,978,000	43,402,000	28,832,000
Water Purification and Filtration
Information as to operating segments
Net sales	44,645,000	44,975,000	132,609,000	129,699,000
Water Purification and Filtration | Operating Segment
Information as to operating segments
Operating income	6,934,000	7,540,000	22,336,000	23,317,000
Healthcare Disposables
Information as to operating segments
Net sales	29,779,000	24,754,000	83,157,000	79,288,000
Healthcare Disposables | Operating Segment
Information as to operating segments
Operating income	6,162,000	3,432,000	18,195,000	14,255,000
Dialysis
Information as to operating segments
Net sales	7,387,000	6,970,000	24,995,000	21,770,000
Dialysis | Operating Segment
Information as to operating segments
Operating income	$ 1,795,000	1,620,000	$ 6,216,000	4,551,000
Other.
Information as to operating segments
Net sales		1,075,000		4,356,000
Other. | Operating Segment
Information as to operating segments
Operating income		$ 211,000		$ 1,118,000