Stock Based Compensation (Details) (USD $)	3 Months Ended		9 Months Ended			12 Months Ended
	Oct. 26, 2014	Oct. 27, 2013	Oct. 26, 2014		Oct. 27, 2013	Jan. 26, 2014
Share-based Compensation
Cost of revenue	$ 3,021,000	$ 3,090,000	$ 8,596,000		$ 7,911,000
Research and development	22,680,000	20,902,000	64,636,000		61,392,000
Sales, general and administrative	15,734,000	10,307,000	42,139,000		30,788,000
Stock-based compensation expense	41,435,000	34,299,000	115,371,000		100,091,000
Stock Options
Stock options beginning balance (in shares)			32,504,000
Stock Options granted (in shares)			86,000
Stock options exercised (in shares)			(7,945,000)
Stock options cancelled (in shares)			(1,361,000)
Stock options ending balance (in shares)	23,284,000		23,284,000			32,504,000
Weighted average exercise price of stock options at beginning of period			$ 14.22
Weighted average exercise price of stock options granted			$ 18.66
Weighted average exercise price of stock options exercised			$ 12.59
Weighted average exercise price of stock options cancelled			$ 19.49
Weighted average exercise price of stock options at end of period	$ 14.48		$ 14.48			$ 14.22
RSUs/PSUs
RSUs/PSUs beginning balance (in shares)			18,852,000
RSUs and PSUs granted (in shares)			12,506,000	[1]
RSUs/PSUs vested (in shares)			(7,138,000)
RSUs/PSUs cancelled (in shares)			(1,089,000)
RSUs/PSUs ending balance (in shares)	23,131,000		23,131,000			18,852,000
Weighted average grant date fair value of RSUs/PSUs at beginning of period			$ 13.82
Weighted average grant-date fair value of RSUs and PSUs			$ 17.63
Weighted average grant-date fair value of RSUs/PSUs vested			$ 13.75
Weighted average grant date fair value of RSUs/PSUs cancelled			$ 14.21
Weighted average grant date fair value of RSUs/PSUs at end of period	$ 15.88		$ 15.88			$ 13.82
Minimum number of PSUs issuable	1,300,000		1,300,000
Maximum number of PSUs issuable	2,500,000		2,500,000
Stock-based compensation expense related to equity awards not expected to vest			35,200,000
Aggregate amount of unearned stock-based compensation expense related to equity awards, adjusted for estimated forfeitures	$ 322,600,000		$ 322,600,000			$ 241,300,000
Unearned stock-based compensation expense related to stock options weighted average amortization period (in years)			2 years 0 months 0 days			2 years 6 months 0 days
Unearned stock-based compensation expense related to RSUs/PSUs weighted average amortization period (in years)			3 years 0 months 0 days			2 years 8 months 12 days

[1] Includes the total number of PSUs issuable if the maximum corporate financial performance target level for fiscal year 2015 is achieved. Depending on the actual level of achievement of the corporate performance goal at the end of fiscal year 2015, the range of PSUs issued could be from 1.3 million to 2.5 million shares. The PSUs were granted during the first quarter of fiscal year 2015 to our CEO and senior management as approved by our Compensation Committee.