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Income Taxes - Summary of Changes in the Valuation Allowance (Details) - USD ($) $ in Thousands | 12 Months Ended
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Jan. 28, 2018 | Jan. 29, 2017 | Jan. 31, 2016
Income Tax Disclosure [Abstract] |  |  |
Beginning balance | $ 82,961 | $ 77,383 | $ 75,536
Additions | 74 | 5,578 | 9,055
Releases | (41,985) | 0 | (7,208)
Ending balance | $ 41,050 | $ 82,961 | $ 77,383

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- Definition Valuation Allowance Additions + References No definition available. + Details
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Balance Type: | credit
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- Definition Valuation Allowance Releases + References No definition available. + Details
Name: | smtc_ValuationAllowanceReleases
Namespace Prefix: | smtc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
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