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Stock-Based Compensation (Summary Of The Activity For Restricted Shares Awards) (Details) (Restricted Stock [Member], USD $)
In Thousands, except Per Share data, unless otherwise specified
6 Months Ended
Jul. 31, 2011
years
Restricted Stock [Member]
 
Beginning balance, Shares 135
Vested, Shares (71)
Cancelled/forfeited, Shares (6)
Ending balance, Shares 58
Beginning balance, Weighted average fair value (per share) $ 14.44
Vested, Weighted average fair value (per share) $ 13.82
Cancelled/forfeited, Weighted average fair value (per share) $ 15.78
Ending balance, Weighted average fair value (per share) $ 15.06
Vested, Aggregate intrinsic value $ 1,725 [1]
Beginning balance, Aggregate unrecognized compensation 984
Ending balance, Aggregate unrecognized compensation $ 431
Beginning balance, Weighted average period over which expected to be recognized (in years) 0.8
Ending balance, Weighted average period over which expected to be recognized (in years) 0.5
[1] Represents the value of Semtech stock on the date that the restricted stock vested.