Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Jul. 31, 2013
Income Tax Disclosure [Abstract]
Effective tax rate	29.00%	33.00%
Effective tax rate exluding the impact of discrete tax items	34.00%	35.00%
Federal statutory income tax rate	35.00%	35.00%
Total amount of unrecognized tax benefits			$ 39
Unrecognized tax benefits, net of related deferred tax assets			27
Favorable net impact to income tax expense due to recognition of tax benefits			$ 27