Description of Business and Summary of Significant Accounting Policies (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2012	Jan. 31, 2011	Jul. 31, 2011 Accounts Receivable [Member] customers	Jan. 31, 2012 Sales [Member] customers	Jan. 31, 2011 Sales [Member] customers	Jan. 31, 2012 Sales [Member] customers	Jan. 31, 2011 Sales [Member] customers
Weighted Average Number of Shares Outstanding, Diluted	306	318	307	322
Percentage of gross accounts receivable represented by one retail customer	13.00%
Numerator:
Net income (loss)	$ 118	$ 73	$ 54	$ 3
Shares used in diluted per share amounts:
Weighted average common shares outstanding	297	308	298	312
Basic and diluted net income (loss) per share:
Basic net income (loss) per share	$ 0.4	$ 0.24	$ 0.18	$ 0.01
Diluted net income (loss) per share	$ 0.39	$ 0.23	$ 0.18	$ 0.01
Weighted average stock options and restricted stock units excluded from calculation due to anti-dilutive effect	3	0	3	1
Number of customers accounted for more than ten percent of concentration risk					0	0	0	0	0
Incremental Common Shares Attributable to Share-based Payment Arrangements	9	10	9	10