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Stock-Based Compensation (Summary of the Activity for Restricted Stock Awards) (Details) (Restricted Stocks [Member], USD $)
In Thousands, except Per Share data, unless otherwise specified
6 Months Ended 12 Months Ended
Jul. 29, 2012
Y
Jan. 29, 2012
Y
Restricted Stocks [Member]
   
Number of Shares    
Beginning balance 32  
Restricted stocks granted 0  
Restricted stocks vested (32)  
Restricted stocks cancelled 0  
Ending balance 0 32
Weighted Average Grant Date Fair Value (per share)    
Beginning balance $ 14.57  
Restricted stocks vested $ 14.57  
Ending balance $ 0.00 $ 14.57
Aggregate Intrinsic Value    
Restricted stocks vested $ 902 [1]  
Aggregate Unrecognized Compensation    
Beginning balance 81  
Ending balance $ 0 $ 81
Weighted Average Period Over Which Expected to be Recognized (in years)    
Weighted average period over which expected to be recognized (in years) 0.0 0.1
[1] Represents the value of Semtech stock on the date that the restricted stock vested.