Income Taxes - Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Expected statutory tax	35.00%	35.00%	35.00%
Differential attributable to:
Foreign operations	0.00%	0.60%	1.20%
State and local taxes	3.90%	3.20%	3.40%
Domestic production deduction	(2.70%)	(2.30%)	(2.40%)
Acquisition related items, net	0.10%	0.00%	(1.60%)
Loss on sale of business	0.00%	0.00%	1.10%
R&E tax credit	(1.40%)	(1.10%)	(0.50%)
Change in foreign tax rates	0.00%	(0.40%)	0.00%
Excess tax benefits	(2.20%)	0.00%	0.00%
Other	0.10%	1.20%	0.90%
Consolidated effective tax rate (as a percent)	32.80%	36.20%	37.10%
Share-based compensation, excess tax benefit, amount	$ 2,241	$ 1,179