Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2012	Jan. 31, 2011	Jul. 31, 2011
Income Taxes (Textuals)
Effective tax rate	34.00%	28.00%	33.00%	36.00%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	35.00%	35.00%	35.00%	35.00%
Income Tax Expense (Benefit)	$ 61	$ 29	$ 27	$ (12)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	179	102	81	(9)
Discrete Tax Benefit Due To Changes In Federal Tax Law		9
Total amount of unrecognized tax benefits					41
Unrecognized tax benefits net of related deferred tax assets					35
Favourable net impact to income tax expense due to recognition of tax benefits					$ 35

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

The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.

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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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