Condensed Consolidated Statements of Operations - USD ($)
 3 Months Ended 6 Months Ended
Jan. 31, 2016
Jan. 31, 2015
Jan. 31, 2016
Jan. 31, 2015
Income Statement [Abstract]        
Net sales $ 70,323,000 $ 81,802,000 $ 134,440,000 $ 158,193,000
Cost of sales 40,885,000 43,927,000 76,800,000 84,993,000
Gross profit 29,438,000 37,875,000 57,640,000 73,200,000
Expenses:        
Selling, general and administrative 15,053,000 16,026,000 30,379,000 31,552,000
Research and development 7,663,000 9,666,000 15,603,000 19,685,000
Acquisition plan expenses 2,337,000 0 3,729,000 0
Amortization of intangibles 1,196,000 1,560,000 2,572,000 3,121,000
Total operating expenses 26,249,000 27,252,000 52,283,000 54,358,000
Operating income 3,189,000 10,623,000 5,357,000 18,842,000
Other expenses (income):        
Interest expense 73,000 69,000 148,000 334,000
Interest income and other (110,000) (90,000) (222,000) (174,000)
Income before provision for income taxes 3,226,000 10,644,000 5,431,000 18,682,000
Provision for income taxes 750,000 3,059,000 1,516,000 5,872,000
Net income $ 2,476,000 $ 7,585,000 $ 3,915,000 $ 12,810,000
Net income per share (See Note 4):        
Basic (in dollars per share) $ 0.15 $ 0.47 $ 0.24 $ 0.79
Diluted (in dollars per share) $ 0.15 $ 0.46 $ 0.24 $ 0.78
Weighted average number of common shares outstanding – basic (in shares) 16,186,000 16,241,000 16,178,000 16,229,000
Weighted average number of common and common equivalent shares outstanding – diluted (in shares) 16,205,000 16,505,000 16,201,000 16,510,000
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 $ 0.60