Acquisitions - Narrative (Details)				0 Months Ended		3 Months Ended	12 Months Ended					0 Months Ended				12 Months Ended
	Jan. 25, 2015 USD ($)	Jan. 26, 2014 USD ($)	Jan. 27, 2013 USD ($)	Jan. 13, 2015 EnVerv USD ($)	Mar. 20, 2012 Gennum USD ($)	Jan. 27, 2013 Gennum USD ($)	Jan. 26, 2014 Gennum USD ($)	Jan. 27, 2013 Gennum USD ($)	Oct. 28, 2012 Gennum USD ($)	May 27, 2012 Gennum USD ($)	Mar. 20, 2012 Gennum CAD	Mar. 07, 2012 Cycleo USD ($)	Mar. 07, 2012 Cycleo USD ($)	Jan. 13, 2015 Developed technology EnVerv USD ($)	Mar. 20, 2012 Developed technology Gennum USD ($)	Jan. 27, 2013 Selling, general and administrative expenses Gennum USD ($)	Jan. 25, 2015 Wireless, Sensing and Timing USD ($)	Jan. 26, 2014 Wireless, Sensing and Timing USD ($)	Jan. 27, 2013 Wireless, Sensing and Timing USD ($)
Total acquisition consideration				$ 4,900,000	$ 506,500,000							$ 5,000,000
Total acquisition consideration allocated to core technologies					129,863,000									1,400,000	95,100,000
Goodwill	280,319,000	276,898,000	393,584,000	3,400,000	261,891,000	261,900,000		261,900,000	262,800,000								18,428,000	15,007,000	15,007,000
Percentage of outstanding shares acquired					100.00%
Price paid per share											13.55
Long-term debt					347,000,000
Secured term loans, maturity term					5 years
Original issue discount on debt					3,000,000
Post-acquisition compensation expense																9,600,000
Goodwill decrease, purchase accounting adjustments						(900,000)
Transaction and integration expenses							1,700,000	24,800,000
Settled pre-acquisition contingencies related to legal matters										4,200,000
Deferred compensation potential cash payment													$ 16,000,000