Description of Business and Summary of Significant Accounting Policies (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Numerator:
Net income (loss)	$ (21)	$ 13	$ (38)	$ (17)
Shares used in basic per share amounts:
Weighted average common shares outstanding (in shares)	256	257	256	257
Shares used in diluted per share amounts:
Weighted average common shares outstanding (in shares)	256	257	256	257
Dilutive common equivalent shares from stock options and restricted stock awards (in shares)	0	3	0	0
Dilutive weighted average common shares outstanding (in shares)	256	260	256	257
Basic and diluted net income (loss) per share:
Basic net income (loss) per share (in dollars per share)	$ (0.08)	$ 0.05	$ (0.15)	$ (0.07)
Diluted net income (loss) per share (in dollars per share)	$ (0.08)	$ 0.05	$ (0.15)	$ (0.07)
Shares excluded from diluted net income (loss) per share:
Weighted average stock options and restricted stock units that have been excluded from dilutive common equivalent shares outstanding due to their anti-dilutive effect (in shares)	13	4	14	15
One retail customer | Accounts receivable | Credit Concentration Risk
Product Information [Line Items]
Percentage of gross accounts receivable for customer			16.00%