Operating Segments - Results (Details) - USD ($)	3 Months Ended		9 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2017	Apr. 30, 2016
Information as to operating segments
Net sales	$ 192,113,000	$ 173,703,000	$ 564,655,000	$ 485,753,000
Operating income	27,444,000	23,263,000	83,120,000	71,435,000
Interest expense, net	(1,084,000)	(871,000)	(3,303,000)	(2,487,000)
Income before income taxes	26,360,000	22,392,000	79,817,000	68,948,000
Operating Segment
Information as to operating segments
Operating income	35,063,000	31,170,000	107,152,000	90,149,000
General corporate
Information as to operating segments
Operating income	(7,619,000)	(7,907,000)	(24,032,000)	(18,714,000)
Endoscopy
Information as to operating segments
Net sales	100,349,000	91,892,000	288,544,000	244,992,000
Endoscopy | Operating Segment
Information as to operating segments
Operating income	18,514,000	16,279,000	54,853,000	43,402,000
Water Purification and Filtration
Information as to operating segments
Net sales	47,940,000	44,645,000	145,233,000	132,609,000
Water Purification and Filtration | Operating Segment
Information as to operating segments
Operating income	7,842,000	6,934,000	25,167,000	22,336,000
Healthcare Disposables
Information as to operating segments
Net sales	36,177,000	29,779,000	108,256,000	83,157,000
Healthcare Disposables | Operating Segment
Information as to operating segments
Operating income	6,392,000	6,162,000	20,857,000	18,195,000
Dialysis
Information as to operating segments
Net sales	7,647,000	7,387,000	22,622,000	24,995,000
Dialysis | Operating Segment
Information as to operating segments
Operating income	$ 2,315,000	$ 1,795,000	$ 6,275,000	$ 6,216,000