Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Oct. 31, 2012	Oct. 31, 2011	Jul. 31, 2012
Income Taxes (Textuals)
Effective tax rate	32.00%	35.00%
Effective tax rate excluding discrete tax benefits	35.00%
Federal statutory income tax rate	35.00%	35.00%
Total amount of unrecognized tax benefits			$ 38
Unrecognized tax benefits net of related deferred tax assets			28
Favourable net impact to income tax expense due to recognition of tax benefits			$ 28

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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- Definition

Amount of an unrecognized tax benefit that is directly related to a position taken in a tax year that results in a net operating loss carryforward. This amount is presented as a reduction of the related deferred tax asset in the balance sheet if that deferred tax asset is not used. This amount is presented separately from the deferred tax asset for a net operating loss carryforward if this unrelated tax benefit is associated with a different tax position.

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