Schedule of Differences between Income Taxes at Federal Statutory Rate and Actual Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2011
Reconciliation of Statutory Federal Tax Rate [Line Items]
Provision at federal statutory rate	$ 77,691	$ 57,886	$ 46,318
State and local income taxes, net of federal benefit	2,815	846	590
Federal income tax credits and incentives	(2,468)	(831)	(1,697)
Domestic production activities deduction	(7,303)	(5,145)	(4,574)
Change in uncertain tax positions	(718)	1,879	(1,107)
Executive compensation limitation		38
Reduction of excess current tax payable and deferred tax liabilities	13	(1,018)	(48)
Other permanent items	266	298	1,208
Total income tax expense	$ 70,296	$ 53,953	$ 40,690

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Income Tax Reconciliation Other Permanent Items

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Reduction Of Excess Current Tax Payable And Deferred Tax Liabilities

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The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to pretax Income or Loss from continuing operations; income tax expense or benefit may include interest and penalties on tax uncertainties based on the entity's accounting policy.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to the deduction for qualified production activities received under enacted tax laws.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to state and local income tax expense or benefit.

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The sum of the differences between total income tax expense or benefit as reported in the Income Statement and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to changes in all income tax contingencies, whether recorded or adjusted, during the period.

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The sum of the differences between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to tax credits.

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