Information as to Operating Segments and Foreign and Domestic Operations (Details 2) - USD ($)	3 Months Ended								12 Months Ended
	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Information as to operating segments
Net sales	$ 151,255,000	$ 141,508,000	$ 135,430,000	$ 136,811,000	$ 131,377,000	$ 120,058,000	$ 119,042,000	$ 118,272,000	$ 565,004,000	$ 488,749,000	$ 425,026,000
Operating income									80,761,000	70,928,000	63,188,000
Interest expense, net									(2,364,000)	(2,317,000)	(2,834,000)
Other expense									(2,206,000)
Income before income taxes									76,191,000	68,611,000	60,354,000
Identifiable assets	584,031,000				536,145,000				584,031,000	536,145,000	487,671,000
Capital expenditures									12,760,000	13,541,000	6,745,000
Depreciation and amortization									23,957,000	18,886,000	17,263,000
Operating Segment
Information as to operating segments
Operating income									99,240,000	87,026,000	75,880,000
General corporate
Information as to operating segments
Operating income									(18,479,000)	(16,098,000)	(12,692,000)
Identifiable assets	35,320,000				33,190,000				35,320,000	33,190,000	34,828,000
Capital expenditures									234,000	558,000	63,000
Depreciation and amortization									157,000	65,000	14,000
Endoscopy
Information as to operating segments
Net sales									248,654,000	190,440,000	160,317,000
Endoscopy | Operating Segment
Information as to operating segments
Operating income									40,863,000	34,194,000	32,361,000
Identifiable assets	238,799,000				203,582,000				238,799,000	203,582,000	157,340,000
Capital expenditures									7,042,000	6,820,000	3,058,000
Depreciation and amortization									10,729,000	7,001,000	6,374,000
Water Purification and Filtration
Information as to operating segments
Net sales									173,834,000	159,505,000	134,196,000
Water Purification and Filtration | Operating Segment
Information as to operating segments
Operating income									30,606,000	25,750,000	16,381,000
Identifiable assets	138,069,000				126,397,000				138,069,000	126,397,000	123,454,000
Capital expenditures									2,984,000	3,318,000	2,319,000
Depreciation and amortization									5,257,000	4,416,000	3,866,000
Healthcare Disposables
Information as to operating segments
Net sales									106,920,000	101,809,000	90,904,000
Healthcare Disposables | Operating Segment
Information as to operating segments
Operating income									19,904,000	18,720,000	17,576,000
Identifiable assets	145,391,000				138,240,000				145,391,000	138,240,000	137,577,000
Capital expenditures									1,587,000	1,367,000	699,000
Depreciation and amortization									6,354,000	5,968,000	5,500,000
Dialysis
Information as to operating segments
Net sales									31,240,000	30,926,000	33,148,000
Dialysis | Operating Segment
Information as to operating segments
Operating income									6,749,000	7,547,000	8,705,000
Identifiable assets	$ 26,452,000				25,420,000				26,452,000	25,420,000	24,394,000
Capital expenditures									894,000	1,444,000	576,000
Depreciation and amortization									1,382,000	1,142,000	1,188,000
Other.
Information as to operating segments
Net sales									4,356,000	6,069,000	6,461,000
Other. | Operating Segment
Information as to operating segments
Operating income									1,118,000	815,000	857,000
Identifiable assets					$ 9,316,000					9,316,000	10,078,000
Capital expenditures									19,000	34,000	30,000
Depreciation and amortization									$ 78,000	$ 294,000	$ 321,000