Credit Facilities Narrative (Details) (USD $)			9 Months Ended		0 Months Ended											0 Months Ended			0 Months Ended			0 Months Ended			3 Months Ended	12 Months Ended									0 Months Ended					9 Months Ended
	May 02, 2013	Mar. 20, 2012	Oct. 26, 2014 Minimum [Member]	Oct. 26, 2014 Maximum [Member]	May 02, 2013 Base Rate [Member] Minimum [Member]	May 02, 2013 Base Rate [Member] Maximum [Member]	May 02, 2013 LIBOR [Member]	May 02, 2013 LIBOR [Member] Minimum [Member]	May 02, 2013 LIBOR [Member] Maximum [Member]	May 02, 2013 Federal Funds [Member]	May 02, 2013 CDOR [Member]	May 02, 2013 CDOR [Member] Minimum [Member]	May 02, 2013 CDOR [Member] Maximum [Member]	Mar. 20, 2012 Prior credit facilities, Term A Loans [Member]	Mar. 20, 2012 Prior credit facilities, Term B Loans [Member]	Jun. 03, 2013 New credit facilities, Term Loan [Member]	Oct. 26, 2014 New credit facilities, Term Loan [Member]	May 02, 2013 New credit facilities, Term Loan [Member]	Jul. 14, 2014 New credit facilities, Revolving Credit Facility [Member]	Oct. 26, 2014 New credit facilities, Revolving Credit Facility [Member]	May 02, 2013 New credit facilities, Revolving Credit Facility [Member]	May 02, 2013 New credit facilities, Revolving Credit Facility [Member] Minimum [Member]	May 02, 2013 New credit facilities, Revolving Credit Facility [Member] Maximum [Member]	May 02, 2013 New credit facilities [Member]	Jul. 28, 2013 New credit facilities [Member]	Jan. 26, 2014 Prior credit facilities [Member]	May 02, 2013 Prior credit facilities [Member]	Oct. 26, 2014 New credit facilities, Letter of Credit [Member]	May 02, 2013 New credit facilities, Letter of Credit [Member]	Oct. 26, 2014 New credit facilities, Swingline Loans [Member]	May 02, 2013 New credit facilities, Swingline Loans [Member]	Oct. 26, 2014 New credit facilities, Revolving Loans and Non US Dollars LC [Member]	May 02, 2013 New credit facilities, Revolving Loans and Non US Dollars LC [Member]	May 02, 2013 Additional Term Loan or Increase in Revolver [Member] Maximum [Member]	May 02, 2013 Alternative Currencies, Except Canadian [Member]	May 02, 2013 United States of America, Dollars	May 02, 2013 Canada, Dollars	May 02, 2013 Base Rate [Member]	May 02, 2013 CDOR [Member]	Oct. 26, 2014 Through second quarter of fiscal year 2018 [Domain]	Oct. 26, 2014 Beginning third quarter of fiscal year 2018 [Domain]
Prior credit facilities, aggregate principal amount of term loans		$ 350,000,000												$ 100,000,000	$ 250,000,000
Initial carrying amounts														99,500,000	247,500,000
Original issue discount on debt														500,000	2,500,000									1,400,000	600,000
New credit facilities, maximum borrowing capacity	400,000,000																	150,000,000			250,000,000								40,000,000		25,000,000		40,000,000	100,000,000
New credit facilities, amount outstanding	326,600,000																100,600,000	149,300,000		153,000,000	177,300,000							0		0		0
New credit facilities, debt discount expensed																									800,000
Prior credit facilities, repayment of outstanding obligations	327,500,000
New credit facilities, deferred financing cost																								2,200,000
New credit facilities, deferred financing costs expensed																									1,000,000
Deferred finance costs capitalized																								1,200,000			1,700,000
New credit facilities, contractual term																								5 years
Prior credit facilities, loss on modification of debt																										(7,100,000)
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.	(1) the Base Rate 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.	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.	the highest of (a) the prime rate (as published by The Wall Street Journal), (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%.	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					0.25%	1.25%	1.00%	1.25%	2.25%	1.00%	0.10%	1.25%	2.25%
New credit facilities, unused capacity, commitment fee percentage																						0.20%	0.45%
New credit facilities, Interest rate at period end																	1.90%			1.90%
New credit facilities, required quarterly principal payment																																								4,700,000	7,500,000
Principal payments remaining in fiscal year 2015																	4,700,000
Principal payments in fiscal year 2016																	18,800,000
Principal payments in fiscal year 2017																	18,800,000
Principal payments in fiscal year 2018																	24,400,000
Repayments of debt																$ 26,000,000			$ 25,000,000
Interest coverage ratio			3.50
Total leverage ratio				3.00