Credit Facilities - Narrative (Details)		1 Months Ended	12 Months Ended
	May. 02, 2013 USD ($)	Mar. 31, 2015 USD ($)	Jan. 31, 2016 USD ($)	Jan. 25, 2015 USD ($)	Jan. 26, 2014 USD ($)	Oct. 23, 2015 USD ($)
Facilities, maximum borrowing capacity	$ 400,000,000
Facilities, contractual term	5 years
Facilities, amount outstanding	$ 326,600,000
Borrowings under line of credit		$ 35,000,000	$ 35,000,000	$ 5,000,000	$ 327,344,000
Facilities, debt discount	1,400,000
Prior credit facilities, repayment of outstanding obligations	$ 327,500,000
Minimum
Interest coverage ratio			3.50
Maximum
Total leverage ratio			3.00
Base Rate
Description of variable rate basis	the highest of (a) the prime rate, (b) ½ of 1% above the federal funds effective rate or (c) one-month LIBOR (determined with respect to deposits in U.S. Dollars) plus 1%.
Base Rate | Minimum
Margin on variable rate	0.25%
Base Rate | Maximum
Margin on variable rate	1.25%
LIBOR
Basis spread on variable rate	1.00%
LIBOR | Minimum
Margin on variable rate	1.25%
LIBOR | Maximum
Margin on variable rate	2.25%
Federal Funds
Basis spread on variable rate	1.00%
CDOR
Description of variable rate basis	the sum of: (a) the rate determined by Administrative Agent with reference to the arithmetic average of the discount rate quotations of all institutions listed for CAD Dollar-denominated bankers’ acceptances displayed and identified on the “Reuters Screen CDOR Page” and (b) 0.10% per annum.
Basis spread on variable rate	0.10%
CDOR | Minimum
Margin on variable rate	1.25%
CDOR | Maximum
Margin on variable rate	2.25%
Term Loans [Member]
Facilities, maximum borrowing capacity	$ 150,000,000
Facilities, amount outstanding	149,300,000
Facilities, voluntary payment					$ 26,000,000
Revolving Commitments
Facilities, maximum borrowing capacity	250,000,000
Facilities, amount outstanding	$ 177,300,000		$ 181,000,000
Facilities, interest rate at period end			2.31%
Facilities, voluntary payment				$ 25,000,000		$ 12,000,000
Revolving Commitments | Minimum
Facilities, unused capacity, commitment fee percentage	0.20%
Revolving Commitments | Maximum
Facilities, unused capacity, commitment fee percentage	0.45%
New credit facilities, Term Loan
Facilities, interest rate at period end			2.31%
Letter of Credit [Member]
Facilities, maximum borrowing capacity	$ 40,000,000
Facilities, amount outstanding			$ 0
Swingline Loans [Member]
Facilities, maximum borrowing capacity	25,000,000
Facilities, amount outstanding			0
Foreign Line of Credit [Member]
Facilities, maximum borrowing capacity	40,000,000
Additional Term Loan or Increase in Revolver [Member]
Facilities, maximum borrowing capacity	$ 100,000,000
Revolving Loans and Non US Dollars LC [Member]
Facilities, amount outstanding			$ 0
United States of America, Dollars
Description of variable rate basis	(1) the Base Rate (as defined below) plus a margin ranging from 0.25% to 1.25% depending upon Semtech’s consolidated leverage ratio or (2) LIBOR (determined with respect to deposits in U.S. Dollars) for an interest period to be selected by Semtech plus a margin ranging from 1.25% to 2.25% depending upon Semtech’s consolidated leverage ratio.
Alternative Currencies, Except Canadian
Description of variable rate basis	a rate per annum equal to LIBOR (determined with respect to deposits in the applicable Alternative Currency) for an interest period to be selected by Semtech plus a margin ranging from 1.25% to 2.25% depending upon Semtech’s consolidated leverage ratio.
Canada, Dollars
Description of variable rate basis	a rate per annum equal to the CDOR Rate for an interest period to be selected by Semtech plus a margin ranging from 1.25% to 2.25% depending upon Semtech’s consolidated leverage ratio.