Stock Based Compensation (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		6 Months Ended		12 Months Ended
		Jul. 31, 2016	Jul. 26, 2015	Jul. 31, 2016	Jul. 26, 2015	Jan. 31, 2016
Share-based Compensation
Cost of revenue		$ 4	$ 3	$ 8	$ 6
Research and development		30	27	59	54
Sales, general and administrative		24	17	44	33
Stock-based compensation expense		$ 58	47	$ 111	93
Stock Options
Stock options beginning balance (in shares)				13.0
Stock Options granted (in shares)				0.0
Stock options exercised (in shares)				(3.0)
Stock options canceled (in shares)				0.0
Stock options ending balance (in shares)		10.0		10.0		13.0
Weighted average exercise price of stock options at beginning of period				$ 14.49
Weighted average exercise price of stock options granted				0
Weighted average exercise price of stock options exercised				14.26
Weighted average exercise price of stock options canceled				0
Weighted average exercise price of stock options at end of period		$ 14.57		$ 14.57		$ 14.49
RSUs, PSUs, and Market-based PSUs
RSUs, PSUs and mkt-based PSUs beginning balance (in shares)				26.0
RSUs, PSUs and mkt-based PSUs granted (in shares)	[1],[2]			4.0
RSUs, PSUs and mkt-based PSUs vested (in shares)				(4.0)
RSUs, PSUs and mkt-based PSUs canceled (in shares)				0.0
RSUs, PSUs, and mkt-based PSUs ending balance (in shares)		26.0		26.0		26.0
Weighted average grant date fair value of RSUs, PSUs and mkt-based PSUs at beginning of period				$ 19.12
Weighted avg grant-date FV of RSUs, PSUs and mkt-based PSUs				33.80
Weighted average grant-date fair value of RSUs, PSUs and mkt-based PSUs vested				16.68
Weighted average grant date fair value of RSUs, PSUs and mkt-based PSUs canceled				0
Weighted avg grant date FV of RSUs, PSUs and mkt-based PSUs at end of period		$ 21.89		$ 21.89		$ 19.12
Minimum number of PSUs issuable		0.0		0.0
Maximum number of PSUs issuable		2.0		2.0
Minimum number of market-based PSUs issuable		0.0		0.0
Maximum number of market-based PSUs issuable		0.3		0.3
Stock-based compensation expense related to equity awards not expected to vest		$ 5	$ 2	$ 17	$ 8
Summary of unearned SBC expense
Aggregate amount of unearned stock-based compensation expense related to equity awards, adjusted for estimated forfeitures		$ 392		$ 392		$ 381
Employee Stock Option
Summary of unearned SBC expense
Estimated weighted average amortization period				9 months 18 days		1 year 1 month 6 days
RSUs, PSUs, and Market-based PSUs
Summary of unearned SBC expense
Estimated weighted average amortization period				2 years 7 months 6 days		2 years 8 months 12 days
Employee Stock Purchase Plan
Summary of unearned SBC expense
Estimated weighted average amortization period				7 months 5 days		8 months 12 days

[1] Includes PSUs that will be issued and eligible to vest if the corporate financial performance maximum target level for fiscal year 2017 is achieved. Depending on the actual level of achievement of the corporate performance target at the end of fiscal year 2017, the PSUs issued could range from 0 to 2 million shares.

[2] Includes market-based PSUs that will be issued and eligible to vest if the maximum target for total shareholder return, or TSR, over the 3-year measurement period is achieved. Depending on the ranking of our TSR compared to the respective TSRs of the companies comprising the Standard & Poor’s 500 Index during a 3-year measurement period, the market-based PSUs issued could range from 0 to 0.3 million shares.