Income Taxes (Provision for Income Taxes Differed from Amounts Computed by the U.S. Federal Income Tax Rate) (Details) - USD ($)	12 Months Ended
	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Income Tax Disclosure [Abstract]
Computed expected tax expense	$ 11,901,000	$ 13,477,000	$ 9,623,000
Computed expected tax rate	35.00%	35.00%	35.00%
State and local income taxes, net of Federal benefit	$ 720,000	$ 1,172,000	$ 782,000
State and local income taxes, net of Federal benefit effective tax rate	2.10%	3.10%	2.80%
Nondeductible stock-based compensation	$ 86,000	$ 70,000	$ 71,000
Effective income tax rate reconciliation, nondeductible expense, share-based compensation cost	0.20%	0.20%	0.30%
Domestic production activities deduction	$ (1,030,000)	$ (912,000)	$ (1,344,000)
Effective income tax rate reconciliation, deductions, qualified production activities	(3.00%)	(2.40%)	(4.90%)
Research and experimentation credits	$ (793,000)	$ (506,000)	$ (888,000)
Effective income tax rate reconciliation, tax credits, research	(2.30%)	(1.30%)	(3.20%)
Change in the beginning of the year valuation allowance for deferred tax assets	$ 0	$ 0	$ 693,000
Effective income tax rate reconciliation, change in deferred tax assets valuation allowance	0.00%	0.00%	2.50%
Income tax reconciliation, tax settlements	$ 0	$ 0	$ (141,000)
Effective income tax rate reconciliation, tax settlements	0.00%	0.00%	(0.50%)
Foreign income taxes	$ (372,000)	$ (62,000)	$ 640,000
Effective income tax rate reconciliation, foreign income tax rate differential	(1.10%)	(0.20%)	2.30%
Other	$ 246,000	$ 117,000	$ 249,000
Effective income tax rate reconciliation, other adjustments	0.70%	0.30%	0.90%
Total provision for income taxes	$ 10,758,000	$ 13,356,000	$ 9,685,000
Income tax effective tax rate, continuing operations	31.60%	34.70%	35.20%