Organization and Basis of Presentation	3 Months Ended
Organization and Basis of Presentation	Apr. 26, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation Nature of Business Semtech Corporation (together with its consolidated subsidiaries, the "Company" or "Semtech") is a leading global supplier of high performance analog and mixed-signal semiconductors and advanced algorithms. The end customers for the Company’s products are primarily original equipment manufacturers ("OEMs") that produce and sell electronics. Fiscal Year The Company reports results on the basis of 52 and 53-week periods and ends its fiscal year on the last Sunday in January. The other quarters generally end on the last Sunday of April, July and October. All quarters consist of 13 weeks except for one 14-week period in the fourth quarter of 53-week years. The first quarters of fiscal years 2021 and 2020 each consisted of 13 weeks. Principles of Consolidation The accompanying interim unaudited condensed consolidated financial statements have been prepared by the Company, in accordance with accounting principles generally accepted in the United States ("GAAP") and on the same basis as the audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the fiscal year ended January 26, 2020 ("Annual Report"). The Company’s interim unaudited condensed consolidated statements of income are referred to herein as the "Statements of Income." The Company’s interim unaudited condensed consolidated balance sheets are referred to herein as the "Balance Sheets" and interim unaudited condensed consolidated statements of cash flows as the "Statements of Cash Flows." In the opinion of the Company, these interim unaudited condensed consolidated financial statements contain all adjustments (consisting of normal recurring adjustments) necessary to present fairly, in all material respects, the financial position of the Company for the interim periods presented. All intercompany balances have been eliminated. Because the interim unaudited condensed consolidated financial statements do not include all of the information and notes required by GAAP for a complete set of consolidated financial statements, they should be read in conjunction with the audited consolidated financial statements and notes included in the Company's Annual Report. The results reported in these interim unaudited condensed consolidated financial statements should not be regarded as indicative of results that may be expected for any subsequent period or for the entire year. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Correction of Immaterial Errors During the fourth quarter of fiscal year 2020, management identified certain immaterial errors related to share-based compensation expense of market-based awards granted during fiscal years 2018, 2019 and 2020. The errors resulted from adjustments to the grant date fair value of the market-based awards that were incorrectly accounted for as performance-based awards. The Company has corrected its consolidated financial statements for these errors for the impacted prior periods presented in this Quarterly Report on Form 10-Q. Refer to Note 16 for a discussion of the Company's assessment of the errors and impact on its consolidated financial statements. Recently Adopted Accounting Guidance In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2016-13, Financial Instruments–Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments. This guidance requires financial assets measured at amortized cost basis to be presented at the net amount expected to be collected. It also requires credit losses on available-for-sale debt securities to be presented as an allowance, rather than reducing the carrying amount. ASU 2016-13 is effective for fiscal years beginning after December 15, 2019, and for interim periods within those fiscal years. The Company adopted ASU 2016-13 in the first quarter of fiscal year 2021, resulting in a $0.3 million reduction to beginning retained earnings, net of tax, and the recognition of a $0.4 million credit loss reserve. Accounting Guidance Issued, but not yet Adopted as of April 26, 2020 In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes, which modifies Accounting Standards Codification ("ASC") 740 to simplify the accounting for income taxes. This guidance impacts the accounting for hybrid tax regimes, the tax basis step-up in goodwill obtained in a transaction that is not a business combination, separate financial statements of legal entities not subject to tax, the intraperiod tax allocation exception to the incremental approach, ownership changes in investments from a subsidiary to an equity method investment and vice versa, interim period accounting for enacted changes in tax law and the year-to-date loss limitation in interim period tax accounting. This guidance is effective for fiscal years beginning after December 15, 2020, and interim periods within this those fiscal years, with early adoption permitted. The Company will adopt this guidance in the first quarter of fiscal year 2022 and is still evaluating the impact on its consolidated financial statements.