Consolidated Statements of Operations - USD ($)	12 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018
Income Statement [Abstract]
Net sales	$ 616,715,000	$ 671,797,000	$ 570,589,000
Cost of sales	389,882,000	424,357,000	346,648,000
Gross profit	226,833,000	247,440,000	223,941,000
Expenses:
Selling, general and administrative	117,130,000	128,639,000	113,922,000
Research and development	52,180,000	56,407,000	53,869,000
Amortization of intangibles	21,595,000	18,320,000	21,075,000
Settlement of intellectual property litigation	0	(3,204,000)	0
Acquisition plan expenses	20,754,000	5,871,000	0
Total operating expenses	211,659,000	206,033,000	188,866,000
Operating income	15,174,000	41,407,000	35,075,000
Other expenses (income):
Interest expense	6,054,000	9,245,000	10,195,000
Write-off of deferred financing costs	0	3,217,000	0
Interest (income) and other	(190,000)	35,000	254,000
Income before provision for (benefit from) income taxes	9,310,000	28,910,000	24,626,000
Provision for (benefit from) income taxes	2,290,000	3,869,000	(5,143,000)
Net income	$ 7,020,000	$ 25,041,000	$ 29,769,000
Net income per share:
Basic (in dollars per share)	$ 0.28	$ 1.04	$ 1.25
Diluted (in dollars per share)	$ 0.28	$ 1.03	$ 1.24
Weighted average number of common shares outstanding - basic (in shares)	24,798,000	24,124,000	23,825,000
Weighted average number of common and common equivalent shares outstanding - diluted (in shares)	24,899,000	24,302,000	24,040,000