Condensed Consolidated Statements of Operations - USD ($)	3 Months Ended		9 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2020	Apr. 30, 2019
Income Statement [Abstract]
Net sales	$ 135,121,000	$ 170,448,000	$ 467,042,000	$ 495,425,000
Cost of sales	82,120,000	106,032,000	289,872,000	311,995,000
Gross profit	53,001,000	64,416,000	177,170,000	183,430,000
Expenses:
Selling, general and administrative	32,313,000	33,409,000	93,538,000	97,243,000
Research and development	12,324,000	13,471,000	40,925,000	40,664,000
Amortization of intangibles	5,517,000	4,536,000	15,952,000	13,113,000
Settlement of intellectual property litigation	0	0	0	(3,204,000)
Acquisition plan expenses	5,983,000	1,704,000	14,397,000	4,612,000
Total operating expenses	56,137,000	53,120,000	164,812,000	152,428,000
Operating (loss) income	(3,136,000)	11,296,000	12,358,000	31,002,000
Other expenses:
Interest expense	1,504,000	2,159,000	4,924,000	7,095,000
Write-off of deferred financing costs	0	0	0	3,217,000
Interest (income) and other	108,000	(22,000)	37,000	(7,000)
(Loss) income before (benefit from) provision for income taxes	(4,748,000)	9,159,000	7,397,000	20,697,000
(Benefit from) provision for income taxes	(759,000)	1,547,000	1,503,000	1,791,000
Net (loss) income	$ (3,989,000)	$ 7,612,000	$ 5,894,000	$ 18,906,000
Net (loss) income per share (See Note 6):
Basic (in dollars per share)	$ (0.16)	$ 0.31	$ 0.24	$ 0.79
Diluted (in dollars per share)	$ (0.16)	$ 0.31	$ 0.24	$ 0.78
Weighted average number of common shares outstanding – basic (in shares)	24,982,000	24,192,000	24,730,000	24,074,000
Weighted average number of common and common equivalent shares outstanding – diluted (in shares)	24,982,000	24,330,000	24,892,000	24,263,000