Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2014	Apr. 30, 2013	Jul. 31, 2013
Income Tax Disclosure [Abstract]
Effective tax rate	34.00%	33.00%	34.00%	32.00%
Effective tax rate excluding the impact of discrete tax items			34.00%	34.00%
Federal statutory income tax rate	35.00%	35.00%	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