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Stock-Based Compensation - Summary of the Activity for Employee Stock Unit Awards (Details) - Employee stock unit awards - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
12 Months Ended
Jan. 31, 2016
Jan. 25, 2015
Jan. 26, 2014
Jan. 27, 2013
Number of Units        
Beginning balance (in shares) 2,138 2,195 2,558  
Stock units granted (in shares) 1,032 929 891  
Stock units vested (in shares) (736) (752) (1,026)  
Stock units forfeited (in shares) (402) (234) (228)  
Ending balance (in shares) 2,032 2,138 2,195 2,558
Weighted Averaged Grant Date Fair Value (per unit)        
Beginning balance (in dollars per share) $ 26.43 $ 27.81 $ 23.41  
Weighted average fair value units granted (in dollars per share) 20.79 23.90 30.95  
Stock units vested (in dollars per share) 26.48 25.55 21.34  
Stock units forfeited (in dollars per share) 25.65 26.29 25.81  
Ending balance (in dollars per share) $ 23.70 $ 26.43 $ 27.81 $ 23.41
Aggregate Intrinsic Value        
Aggregate intrinsic value of stock units vested [1] $ 16,175 $ 18,237 $ 31,861  
Aggregate Unrecognized Compensation        
Beginning balance 44,506 49,563 49,374  
Ending balance $ 35,692 $ 44,506 $ 49,563 $ 49,374
Weighted Average Remaining Expense Period (in years)        
Ending Balance 2 years 5 months 2 years 5 months 2 years 6 months 2 years 6 months
[1] Reflects the value of Semtech stock on the date that the stock unit vested.