Schedule of Differences between Income Taxes at Federal Statutory Rate and Actual Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Reconciliation of Statutory Federal Tax Rate [Line Items]
Provision at federal statutory rate	$ 102,513	$ 88,487	$ 77,691
State and local income taxes, net of federal benefit	5,144	3,748	2,815
Federal income tax credits and incentives	(2,207)	(772)	(2,468)
Domestic production activities deduction	(9,519)	(7,947)	(7,303)
Change in uncertain tax positions	(5,650)	(6,631)	(718)
Change in current tax payable and deferred tax liabilities	218	125	13
Other permanent items	387	293	266
Total income tax expense	$ 90,886	$ 77,303	$ 70,296