Stock-Based Compensation - Summary of the Activity for Restricted Stock Awards (Details) (Restricted stock, USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Jan. 25, 2015	Jan. 27, 2013		Jan. 29, 2012
Restricted stock
Number of Shares
Beginning balance (in shares)		32
Restricted stocks granted (in shares)		0
Restricted stocks vested (in shares)		(32)
Restricted stocks cancelled (in shares)		0
Ending balance (in shares)		0		32
Weighted Average Grant Date Fair Value (per share)
Beginning balance (in dollars per share)		$ 14.57
Restricted stocks vested (in dollars per share)		$ 14.57
Restricted stocks cancelled (in dollars per share)
Ending balance (in dollars per share)		$ 0.00		$ 14.57
Aggregate Intrinsic Value
Restricted stocks vested		$ 902	[1]
Aggregate Unrecognized Compensation
Beginning balance		81
Ending balance		$ 0		$ 81
Weighted Average Remaining Expense Period (in years)
Ending Balance	0 years	0 years		0 years 1 month 6 days

[1] Represents the value of Semtech stock on the date that the restricted stock vested.