Schedule of Differences between Income Taxes at Federal Statutory Rate and Actual Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Reconciliation of Statutory Federal Tax Rate [Line Items]
Provision at federal statutory rate	$ 134,160	$ 102,513	$ 88,487
State and local income taxes, net of federal benefit	6,599	5,144	3,748
Federal income tax credits and incentives	(4,194)	(2,207)	(772)
Domestic production activities deduction	(12,609)	(9,519)	(7,947)
Change in uncertain tax positions	611	(5,650)	(6,631)
Change in current tax payable and deferred tax liabilities	103	218	125
Other permanent items	621	387	293
Total income tax expense	$ 125,291	$ 90,886	$ 77,303