Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2015	Apr. 30, 2014	Jul. 31, 2014
Income Taxes [Line Items]
U.S. Federal statutory tax rate	35.00%	35.00%	35.00%	35.00%
Discrete tax benefit	$ 2.9		$ 3.7	$ 10.6
Discrete tax items, favorable changes in reserves for uncertain tax positions	3.0	0.2	3.0
Discrete tax items, miscellaneous favorables/unfavorable	(0.1)	0.4	(0.1)
Remeasurement of tax reserves on a reduction in uncertain federal tax credits for R&D			0.8	0.9
Discrete tax items, unfavorable adjustment to a deferred item related to equity compensation		0.6
Reduction of taxes from change in branch accounting for Canadian operations				8.8
Other items				0.9
Unrecognized tax benefits, accrued interest and penalties	0.3		0.3		0.6
Unrecognized tax benefits, for uncertain tax positions	$ 4.4us-gaap_UnrecognizedTaxBenefits		$ 4.4us-gaap_UnrecognizedTaxBenefits

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Income Tax Reconciliation, Expiration Of Statute Of Limitations And Related Interest

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of income tax expense (benefit) from continuing operations attributable to an adjustment of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity.

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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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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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