Operating Segments - Results (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Information as to operating segments
Net sales	$ 184,817,000	$ 158,271,000	$ 372,542,000	$ 312,050,000
Operating income	28,613,000	24,396,000	55,676,000	48,172,000
Interest expense, net	(1,126,000)	(871,000)	(2,219,000)	(1,616,000)
Income before income taxes	27,487,000	23,525,000	53,457,000	46,556,000
Operating Segment
Information as to operating segments
Operating income	36,399,000	29,660,000	72,089,000	58,979,000
General corporate
Information as to operating segments
Operating income	(7,786,000)	(5,264,000)	(16,413,000)	(10,807,000)
Endoscopy
Information as to operating segments
Net sales	94,367,000	81,458,000	188,195,000	153,100,000
Endoscopy | Operating Segment
Information as to operating segments
Operating income	18,778,000	14,664,000	36,339,000	27,123,000
Water Purification and Filtration
Information as to operating segments
Net sales	47,420,000	43,252,000	97,293,000	87,964,000
Water Purification and Filtration | Operating Segment
Information as to operating segments
Operating income	8,405,000	7,589,000	17,325,000	15,402,000
Healthcare Disposables
Information as to operating segments
Net sales	35,280,000	26,026,000	72,079,000	53,378,000
Healthcare Disposables | Operating Segment
Information as to operating segments
Operating income	7,069,000	5,673,000	14,465,000	12,033,000
Dialysis
Information as to operating segments
Net sales	7,750,000	7,535,000	14,975,000	17,608,000
Dialysis | Operating Segment
Information as to operating segments
Operating income	$ 2,147,000	$ 1,734,000	$ 3,960,000	$ 4,421,000