Guarantees (Details) (USD $)	12 Months Ended
	Jan. 25, 2015		Jan. 26, 2014		Jan. 27, 2013		Jan. 30, 2011
Notes to financial statements [Abstract]
Cumulative Net Warranty charge	$ 475,900,000
Release of warranty accrual	7,800,000
Estimated product warranty liabilities
Balance at beginning of period	7,571,000	[1]	14,874,000	[1]			18,406,000	[1]
Additions	5,441,000		6,786,000		5,738,000
Deductions	(5,489,000)	[2]	(14,089,000)	[2]	(9,270,000)	[2]
Balance at end of period	7,523,000		7,571,000	[1]	14,874,000	[1]	18,406,000	[1]
Remaining amount of the warranty accrual associated with incremental repair and replacement costs from a weak die/packaging material set			9,600,000		13,200,000
Payments related to warranty accrual			$ 1,800,000		$ 3,000,000

[1] Includes a balance of $9.6 million and $13.2 million for fiscal years 2014 and 2013, respectively, for the remaining amount of the warranty accrual associated with incremental repair and replacement costs from a weak die/packaging material set, which we recorded prior to fiscal year 2013.

[2] Includes $1.8 million and $3.0 million for fiscal years 2014 and 2013, respectively, in payments related to weak die/packaging set warranty accrual recorded prior to fiscal year 2013, and $7.8 million related to the release of the final unclaimed portion of that accrual during fiscal year 2014.