Interest Coverage Ratio

No definition available.

Name:	smtc_InterestCoverageRatio
Namespace Prefix:	smtc_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Prior credit facilities, repayment of outstanding obligations

+ References

No definition available.

+ Details

Name:	smtc_Priorcreditfacilitiesrepaymentofoutstandingobligations
Namespace Prefix:	smtc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Total Leverage Ratio

+ References

No definition available.

+ Details

Name:	smtc_TotalLeverageRatio
Namespace Prefix:	smtc_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentDescriptionOfVariableRateBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of the required periodic payments applied to principal.

+ References

+ Details

Name:	us-gaap_DebtInstrumentPeriodicPaymentPrincipal
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

+ Details

Name:	us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the remainder of the fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

+ Details

Name:	us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

Name:	us-gaap_ProceedsFromLongTermLinesOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=smtc_FederalFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=smtc_CdorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=smtc_SwinglineLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=smtc_AdditionalTermLoanOrIncreaseInRevolverMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=smtc_AlternativeCurrenciesExceptCanadianMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_ForeignLineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CurrencyAxis=currency_USD
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CurrencyAxis=currency_CAD
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	smtc_FiscalYearPeriodAxis=smtc_Throughsecondquarteroffiscalyear2018Domain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	smtc_FiscalYearPeriodAxis=smtc_Beginningthirdquarteroffiscalyear2018Domain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Credit Facilities - Narrative (Details)			6 Months Ended
Credit Facilities - Narrative (Details)	Mar. 04, 2015 USD ($)	May 02, 2013 USD ($)	Jul. 31, 2016 USD ($)	Jul. 26, 2015 USD ($)
Facilities, maximum borrowing capacity		$ 400,000,000
Facilities, amount outstanding		326,600,000
Facilities, debt discount		1,400,000
Prior credit facilities, repayment of outstanding obligations		$ 327,500,000
Borrowings under line of credit	$ 35,000,000		$ 0	$ 35,000,000
Minimum [Member]
Interest coverage ratio			3.50
Maximum [Member]
Total leverage ratio			3.00
Base Rate [Member]
Description of variable rate basis		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%.
Base Rate [Member] \| Minimum [Member]
Basis spread on variable rate		0.25%
Base Rate [Member] \| Maximum [Member]
Basis spread on variable rate		1.25%
LIBOR [Member]
Basis spread on variable rate		1.00%
LIBOR [Member] \| Minimum [Member]
Basis spread on variable rate		1.25%
LIBOR [Member] \| Maximum [Member]
Basis spread on variable rate		2.25%
Federal Funds [Member]
Basis spread on variable rate		1.00%
CDOR [Member]
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 [Member] \| Minimum [Member]
Basis spread on variable rate		1.25%
CDOR [Member] \| Maximum [Member]
Basis spread on variable rate		2.25%
Term Loans [Member]
Facilities, maximum borrowing capacity		$ 150,000,000
Facilities, amount outstanding		149,300,000	$ 67,800,000
Facilities, Interest rate at period end			2.75%
Principal payments remaining in fiscal year 2017			$ 9,400,000
Principal payments in fiscal year 2018			24,400,000
Revolving Commitments [Member]
Facilities, maximum borrowing capacity		250,000,000
Facilities, amount outstanding		$ 177,300,000	$ 181,000,000
Facilities, Interest rate at period end			2.75%
Revolving Commitments [Member] \| Minimum [Member]
Facilities, unused capacity, commitment fee percentage		0.20%
Revolving Commitments [Member] \| Maximum [Member]
Facilities, unused capacity, commitment fee percentage		0.45%
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
Additional Term Loan or Increase in Revolver [Member]
Facilities, maximum borrowing capacity		$ 100,000,000
Alternative Currencies, Except Canadian [Member]
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.
Alternative Currencies Line of Credit [Member]
Facilities, maximum borrowing capacity		$ 40,000,000
Facilities, amount outstanding			0
United States of America, Dollars
Description of variable rate basis		(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.
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.
Through second quarter of fiscal year 2018 [Domain] \| Term Loans [Member]
Facilities, required quarterly principal payment			4,700,000
Beginning third quarter of fiscal year 2018 [Domain] \| Term Loans [Member]
Facilities, required quarterly principal payment			$ 7,500,000