Condensed Consolidated Statements of Operations - USD ($)	3 Months Ended		6 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Income Statement [Abstract]
Net sales	$ 161,292,000	$ 161,654,000	$ 296,510,000	$ 331,921,000
Cost of sales	105,612,000	101,052,000	190,622,000	207,752,000
Gross profit	55,680,000	60,602,000	105,888,000	124,169,000
Expenses:
Selling, general and administrative	29,462,000	29,374,000	57,002,000	61,225,000
Research and development	12,664,000	13,740,000	24,299,000	28,601,000
Amortization of intangibles	4,795,000	5,229,000	10,361,000	10,435,000
Acquisition plan expenses	3,357,000	6,025,000	94,540,000	8,414,000
Total operating expenses	50,278,000	54,368,000	186,202,000	108,675,000
Operating income (loss)	5,402,000	6,234,000	(80,314,000)	15,494,000
Other expenses (income):
Interest expense	1,418,000	1,616,000	3,715,000	3,420,000
Interest (income) and other	(66,000)	6,000	0	(71,000)
Income (loss) before (benefit from) provision for income taxes	4,050,000	4,612,000	(84,029,000)	12,145,000
(Benefit from) provision for income taxes	(155,000)	1,117,000	(2,394,000)	2,262,000
Net income (loss)	$ 4,205,000	$ 3,495,000	$ (81,635,000)	$ 9,883,000
Net income (loss) per share:
Basic (in dollars per share)	$ 0.17	$ 0.14	$ (3.22)	$ 0.40
Diluted (in dollars per share)	$ 0.17	$ 0.14	$ (3.22)	$ 0.40
Weighted average number of common shares outstanding - basic (in shares)	25,337,000	24,659,000	25,321,000	24,607,000
Weighted average number of common and common equivalent shares outstanding - diluted (in shares)	25,420,000	25,058,000	25,321,000	24,904,000