Consolidated Statements of Operations - USD ($)		12 Months Ended
		Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Income Statement [Abstract]
Net sales		$ 307,289,000	$ 347,150,000	$ 319,797,000
Cost of sales		168,405,000	195,712,000	178,967,000
Gross profit		138,884,000	151,438,000	140,830,000
Expenses:
Selling, general and administrative		62,680,000	67,147,000	63,265,000
Research and development		35,916,000	34,108,000	36,748,000
Amortization of intangibles		6,211,000	6,285,000	6,328,000
Total operating expenses		104,807,000	107,540,000	106,341,000
Operating income		34,077,000	43,898,000	34,489,000
Other expenses (income):
Interest expense		479,000	6,304,000	8,163,000
Interest income and other		(405,000)	(913,000)	(1,167,000)
Income before provision for income taxes		34,003,000	38,507,000	27,493,000
Provision for income taxes		10,758,000	13,356,000	9,685,000
Net income		$ 23,245,000	$ 25,151,000	$ 17,808,000
Net income per share:
Basic (in dollars per share)		$ 1.43	$ 1.58	$ 1.05
Diluted (in dollars per share)	[1]	$ 1.42	$ 1.37	$ 0.97
Weighted average number of common shares outstanding - basic (in shares)		16,203,000	15,943,000	16,963,000
Weighted average number of common and common equivalent shares outstanding - diluted (in shares)		16,418,000	20,906,000	23,064,000
Dividends declared per issued and outstanding common share as of the applicable dividend record date (in dollars per share)		$ 1.20	$ 1.175	$ 1.10

[1] The per share information is computed independently for each quarter and the full year based on the respective weighted average number of common shares outstanding. Therefore, income per share information for the full fiscal year may not equal the total of the quarters within the year.