Guarantees (Details) (USD $)	12 Months Ended
	Jan. 26, 2014		Jan. 27, 2013		Jan. 29, 2012
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	14,874,000	[1]	18,406,000	[1]	107,896,000	[1]
Additions	6,786,000		5,738,000		7,329,000
Deductions	(14,089,000)	[2]	(9,270,000)	[2]	(96,819,000)	[2]
Balance at end of period	7,571,000		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		103,700,000
Payments related to warranty accrual	$ 1,800,000		$ 3,000,000		$ 73,300,000

[1] Includes a balance of $9.6 million, $13.2 million and $103.7 million for fiscal years 2014, 2013 and 2012, 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 2012.

[2] Includes $1.8 million, $3.0 million and $73.3 million for fiscal years 2014, 2013 and 2012, respectively, in payments related to weak die/packaging set warranty accrual recorded prior to fiscal year 2012, and $7.8 million related to the release of the final unclaimed portion of that accrual during fiscal year 2014.