Stock-Based Compensation - Summary of Activity For Stock Settled Non-Employee Directors Stock Unit Awards (Details) - Subject To Share Settlement [Member] - Non-employee director stock unit awards [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		9 Months Ended	12 Months Ended
		Oct. 25, 2015	Jan. 25, 2015
Number of Units
Beginning balance (in shares)		0
Stock units granted (in shares)		24
Stock units vested (in shares)		0
Stock units forfeited (in shares)		0
Ending balance (in shares)		24	0
Weighted Averaged Grant Date Fair Value (per unit)
Beginning balance (in dollars per share)		$ 0.00
Stock units granted (in dollars per share)		19.70
Ending balance (in dollars per share)		$ 19.70	$ 0.00
Aggregate Intrinsic Value
Aggregate intrinsic value of stock units vested	[1]	$ 0
Aggregate Unrecognized Compensation
Beginning balance		0
Ending balance		$ 320	$ 0
Period Over Which Expected to be Recognized (in years)
Weighted average period over which expected to be recognized		7 months	0 months

[1] There was no vesting during the reported period. This value would typically represent the value of Semtech Corporation stock on the date that the restricted stock unit vested.