Information as to Operating Segments and Foreign and Domestic Operations (Details 2) (USD $)	3 Months Ended								12 Months Ended
	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2011
Information as to operating segments
Net sales	$ 113,973,000	$ 105,009,000	$ 106,363,000	$ 99,681,000	$ 98,693,000	$ 97,238,000	$ 97,297,000	$ 93,262,000	$ 425,026,000	$ 386,490,000	$ 321,651,000
Operating income:									63,188,000	52,124,000	31,336,000
Interest expense, net									(2,834,000)	(3,650,000)	(874,000)
Other expense										(605,000)
Income before income taxes									60,354,000	47,869,000	30,462,000
Identifiable assets	487,671,000				434,812,000				487,671,000	434,812,000	321,443,000
Capital expenditures									6,745,000	5,502,000	5,835,000
Depreciation and amortization									17,263,000	15,925,000	12,446,000
Operating Segments
Information as to operating segments
Operating income:									75,880,000	62,770,000	40,274,000
Endoscopy
Information as to operating segments
Net sales									160,317,000	153,224,000	102,484,000
Operating income:									32,361,000	31,083,000	12,419,000
Identifiable assets	157,340,000				153,994,000				157,340,000	153,994,000	46,735,000
Capital expenditures									3,058,000	2,356,000	1,133,000
Depreciation and amortization									6,374,000	6,060,000	1,096,000
Water Purification and Filtration
Information as to operating segments
Net sales									134,196,000	114,609,000	104,308,000
Operating income:									16,381,000	9,819,000	7,408,000
Identifiable assets	123,454,000				112,432,000				123,454,000	112,432,000	112,561,000
Capital expenditures									2,319,000	1,656,000	2,232,000
Depreciation and amortization									3,866,000	3,807,000	3,726,000
Healthcare Disposables
Information as to operating segments
Net sales									90,904,000	76,229,000	70,202,000
Operating income:									17,576,000	12,437,000	9,572,000
Identifiable assets	137,577,000				100,569,000				137,577,000	100,569,000	104,443,000
Capital expenditures									699,000	795,000	1,136,000
Depreciation and amortization									5,500,000	4,490,000	5,923,000
Dialysis
Information as to operating segments
Net sales									33,148,000	35,644,000	38,055,000
Operating income:									8,705,000	8,366,000	9,750,000
Identifiable assets	24,394,000				25,793,000				24,394,000	25,793,000	27,038,000
Capital expenditures									576,000	583,000	652,000
Depreciation and amortization									1,188,000	1,230,000	1,365,000
Other
Information as to operating segments
Net sales									6,461,000	6,784,000	6,602,000
Operating income:									857,000	1,065,000	1,125,000
Identifiable assets	10,078,000				10,944,000				10,078,000	10,944,000	11,350,000
Capital expenditures									30,000	97,000	666,000
Depreciation and amortization									321,000	326,000	307,000
General corporate
Information as to operating segments
General corporate expenses									(12,692,000)	(10,646,000)	(8,938,000)
Identifiable assets	34,828,000				31,080,000				34,828,000	31,080,000	19,316,000
Capital expenditures									63,000	15,000	16,000
Depreciation and amortization									$ 14,000	$ 12,000	$ 29,000