Stock-Based Compensation - Summary of the Activity for Employee Stock Unit Awards (Details) (Employee stock unit awards, USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Jan. 27, 2013		Jan. 29, 2012		Jan. 30, 2011		Jan. 31, 2010
Employee stock unit awards
Number of Units
Beginning balance (in shares)	1,982		2,058		1,410
Stock units granted (in shares)	1,517		810		1,181
Stock units vested (in shares)	(699)		(627)		(404)
Stock units forfeited (in shares)	(242)		(259)		(129)
Ending balance (in shares)	2,558		1,982		2,058		1,410
Weighted Averaged Grant Date Fair Value (per unit)
Beginning balance (in dollars per share)	$ 19.06		$ 16.70		$ 15.72
Stock units granted (in dollars per share)	$ 26.73		$ 22.74		$ 17.62
Stock units vested (in dollars per share)	$ 18.20		$ 16.61		$ 19.20
Stock units forfeited (in dollars per share)	$ 23.65		$ 17.75		$ 19.50
Ending balance (in dollars per share)	$ 23.41		$ 19.06		$ 16.70		$ 15.72
Aggregate Intrinsic Value
Aggregate intrinsic value of stock units vested	$ 18,438	[1]	$ 14,333	[1]	$ 7,749	[1]
Aggregate Unrecognized Compensation
Beginning balance	31,472		29,763		17,713
Ending balance	$ 49,374		$ 31,472		$ 29,763		$ 17,713
Weighted Average Period Over Which Expected to be Recognized (in years)
Ending Balance	2 years 6 months		2 years 4 months 24 days		2 years 8 months 12 days		3 years 4 months 24 days

[1] Reflects the value of Semtech stock on the date that the stock unit vested.