Condensed Consolidated Statements of Operations (USD $)	3 Months Ended		6 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2015	Jan. 31, 2014
Income Statement [Abstract]
Net sales	$ 81,802,000	$ 85,499,000	$ 158,193,000	$ 168,867,000
Cost of sales	43,927,000	48,130,000	84,993,000	95,120,000
Gross profit	37,875,000	37,369,000	73,200,000	73,747,000
Expenses:
Selling, general and administrative	16,026,000	16,349,000	31,552,000	32,547,000
Research and development	9,666,000	8,266,000	19,685,000	16,765,000
Amortization of intangibles	1,560,000	1,582,000	3,121,000	3,164,000
Total operating expenses	27,252,000	26,197,000	54,358,000	52,476,000
Operating income	10,623,000	11,172,000	18,842,000	21,271,000
Other expenses (income):
Interest expense	69,000	1,998,000	334,000	4,016,000
Interest income and other	(90,000)	(228,000)	(174,000)	(501,000)
Income before provision for income taxes	10,644,000	9,402,000	18,682,000	17,756,000
Provision for income taxes	3,059,000	3,419,000	5,872,000	6,468,000
Net income	$ 7,585,000	$ 5,983,000	$ 12,810,000	$ 11,288,000
Net income per share (See Note 5):
Basic (in dollars per share)	$ 0.47	$ 0.37	$ 0.79	$ 0.70
Diluted (in dollars per share)	$ 0.46	$ 0.32	$ 0.78	$ 0.60
Weighted average number of common shares outstanding – basic (in shares)	16,241,000	15,970,000	16,229,000	16,212,000
Weighted average number of common and common equivalent shares outstanding – diluted (in shares)	16,505,000	22,487,000	16,510,000	22,552,000
Dividends declared per issued and outstanding common share as of the applicable dividend record date (in dollars per share)	$ 0.30	$ 0.30	$ 0.60	$ 0.575