Valuation and Qualifying Accounts and Reserves (Details) - USD ($)		12 Months Ended
		Jul. 31, 2019		Jul. 31, 2018	Jul. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Charged to cost and expenses		$ 1,136,000		$ 573,000	$ 497,000
Charged to cost and expenses		6,015,000		5,628,000	2,900,000
Allowance for doubtful accounts receivable:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		1,761,000		1,300,000	1,029,000
Charged to cost and expenses	[1]	1,136,000		573,000	497,000
Charged to other accounts - describe		0		0	0
Transfers (deductions) - describe	[2]	(1,030,000)		(112,000)	(226,000)
Balance at end of period		1,867,000		1,761,000	1,300,000
Inventory reserves:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		17,427,000		16,019,000	16,198,000
Charged to cost and expenses	[3]	6,015,000		5,628,000	2,900,000
Charged to other accounts - describe		0		0	0
Transfers (deductions) - describe	[4]	(3,746,000)		(4,220,000)	(3,079,000)
Balance at end of period		19,696,000		17,427,000	16,019,000
Valuation allowance for deferred tax assets:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		11,854,000		8,633,000	9,624,000
Charged to cost and expenses	[5]	58,000		3,221,000	324,000
Charged to other accounts - describe		656,000	[6]	0	121,000	[6]
Transfers (deductions) - describe		0		0	(1,436,000)	[6]
Balance at end of period		$ 12,568,000		$ 11,854,000	$ 8,633,000

[1] Provision for doubtful accounts.

[2] Write-off of uncollectible receivables.

[3] Provision for excess and obsolete inventory.

[4] Write-off of inventory.

[5] Change in valuation allowance.

[6] Acquisition related valuation allowance charged to (deducted from) goodwill.