Description of Business and Summary of Significant Accounting Policies (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2012 Accounts Receivable [Member] customers	Jul. 31, 2011 Accounts Receivable [Member] customers	Apr. 30, 2012 Sales [Member] customers	Apr. 30, 2011 Sales [Member] customers	Apr. 30, 2012 Sales [Member] customers	Apr. 30, 2011 Sales [Member] customers
Numerator:
Net income	$ 734	$ 688	$ 788	$ 691
Shares used in basic per share amounts:
Weighted average common shares outstanding	295	303	297	309
Shares used in diluted per share amounts:
Weighted average common shares outstanding	295	303	297	309
Dilutive common equivalent shares from stock options and restricted stock awards	8	10	9	10
Dilutive weighted average common shares outstanding	303	313	306	319
Basic and diluted net income per share:
Basic net income per share	$ 2.49	$ 2.27	$ 2.65	$ 2.23
Diluted net income per share	$ 2.42	$ 2.20	$ 2.58	$ 2.16
Weighted average stock options and restricted stock units excluded from calculation due to anti-dilutive effect	0	1	3	0
Number of customers accounted for more than ten percent of concentration risk					0	0	0	0	0	0