Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010
Compensation and Retirement Disclosure [Abstract]
Maximum percent of salary bonus and commission eligible for executive deferred compensation plan	75.00%
Executive deferred compensation plan liabilities	$ 56	$ 50
Maximum percent of pre tax salary eligible for contribution to employee plan	30.00%
Additional employer contribution for next six percent of salary in percent	125.00%
Additional salary contributed by the employee, in percent	6.00%
Matching contributions	$ 43	$ 34	$ 32