Description of Business and Summary of Significant Accounting Policies (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 31, 2017 USD ($) customer $ / shares shares	Jan. 31, 2016 USD ($) customer $ / shares shares	Jan. 31, 2017 USD ($) customer $ / shares shares	Jan. 31, 2016 USD ($) customer $ / shares shares	Jul. 31, 2016 customer
Numerator:
Net income (loss) from continuing operations | $	$ 13	$ 29	$ (17)	$ (2)
Net loss from discontinued operations | $	0	(5)	0	(5)
Net income (loss) | $	$ 13	$ 24	$ (17)	$ (7)
Shares used in basic per share amounts:
Weighted average common shares outstanding | shares	257	263	257	267
Shares used in diluted per share amounts:
Weighted average common shares outstanding | shares	257	263	257	267
Dilutive common equivalent shares from stock options and restricted stock awards (in shares) | shares	3	3	0	0
Dilutive weighted average common shares outstanding (in shares) | shares	260	266	257	267
Basic and diluted net income (loss) per share:
Basic net income (loss) per share from continuing operations (in USD per share) | $ / shares	$ 0.05	$ 0.11	$ (0.07)	$ (0.01)
Basic net income (loss) per share from discontinued operations (in USD per share) | $ / shares	0	(0.02)	0	(0.02)
Basic net income (loss) per share (in USD per share) | $ / shares	0.05	0.09	(0.07)	(0.03)
Diluted net income (loss) per share from continuing operations (in USD per share) | $ / shares	0.05	0.11	(0.07)	(0.01)
Diluted net income (loss) per share from discontinued operations (in USD per share) | $ / shares	0	(0.02)	0	(0.02)
Diluted net income (loss) per share (in USD per share) | $ / shares	$ 0.05	$ 0.09	$ (0.07)	$ (0.03)
Weighted average stock options and restricted stock units that would have been included in the computation of dilutive common equivalent shares outstanding if net income had been reported in the period | shares	0	0	11	13
Shares excluded from computation of diluted net income (loss) per share:
Weighted average stock options and restricted stock units excluded from computation due to anti-dilutive effect | shares	4	2	4	2
Customer concentration risk | Sales revenue, net
Concentration Risk [Line Items]
Concentration risk, number of customers | customer	0	0	0	0
Customer concentration risk | Accounts receivable
Concentration Risk [Line Items]
Concentration risk, number of customers | customer			1		0