Credit Facilities - Narrative (Details) (USD $)	12 Months Ended	0 Months Ended	6 Months Ended
	Jan. 25, 2015	May 02, 2013	Jul. 27, 2014	Mar. 20, 2012	Jun. 03, 2013	Jul. 15, 2014	Oct. 27, 2013
Prior credit facilities, aggregate principal amount of term loans				$ 350,000,000
New credit facilities, maximum borrowing capacity		400,000,000
New credit facilities, amount outstanding		326,600,000
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%
Prior credit facilities, Term A Loans
Prior credit facilities, aggregate principal amount of term loans				100,000,000
Initial carrying amounts				(99,500,000)
Original issue discount on debt				500,000
Prior credit facilities, Term B Loans
Prior credit facilities, aggregate principal amount of term loans				250,000,000
Initial carrying amounts				(247,500,000)
Original issue discount on debt				2,500,000
New credit facilities, Term Loan
New credit facilities, maximum borrowing capacity		150,000,000
New credit facilities, amount outstanding		149,300,000
New credit facilities, interest rate at period end	1.92%
New credit facilities, early term loan prepayment					26,000,000
New credit facilities, Revolving Credit Facility
New credit facilities, maximum borrowing capacity		250,000,000
New credit facilities, amount outstanding	158,000,000	177,300,000
New credit facilities, interest rate at period end	1.918%
New credit facilities, early term loan prepayment						25,000,000
New credit facilities, Revolving Credit Facility | Minimum
New credit facilities, unused capacity, commitment fee percentage		0.20%
New credit facilities, Revolving Credit Facility | Maximum
New credit facilities, unused capacity, commitment fee percentage		0.45%
New credit facilities
New credit facilities, debt discount		1,400,000
New credit facilities, debt discount expensed			800,000
New credit facilities, debt discount capitalized		600,000
New credit facilities, deferred financing costs		2,200,000
New credit facilities, deferred financing costs expensed			1,000,000
Deferred finance costs capitalized		1,200,000
New credit facilities, contractual term		5 years
Prior credit facilities
Deferred finance costs capitalized		1,700,000
Prior credit facilities, gains (losses) on modification of debt	(7,100,000)
New credit facilities, Letter of Credit
New credit facilities, maximum borrowing capacity		40,000,000
New credit facilities, amount outstanding							0
New credit facilities, Swingline Loans
New credit facilities, maximum borrowing capacity		25,000,000
New credit facilities, amount outstanding							0
New credit facilities, Revolving Loans and Non US Dollars LC
New credit facilities, maximum borrowing capacity		40,000,000
New credit facilities, amount outstanding							0
Additional Term Loan or Increase in Revolver | Maximum
New credit facilities, maximum borrowing capacity		100,000,000
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.