Basis of Presentation and Summary of Significant Accounting Policies	9 Months Ended
	Oct. 02, 2021
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited interim Condensed Consolidated Financial Statements include the accounts of BlueLinx Holdings Inc. and its wholly owned subsidiaries (the “Company”). We derived the condensed consolidated balance sheet at October 2, 2021, from the audited consolidated financial statements included in our Annual Report on Form 10-K for the fiscal year ended January 2, 2021 (the “Fiscal 2020 Form 10-K”), as filed with the Securities and Exchange Commission on March 3, 2021. In the opinion of our management, the condensed consolidated financial statements reflect all adjustments, which are of a normal recurring nature, necessary for a fair presentation of our statements of operations and comprehensive income for the three and nine months ended October 2, 2021, and September 26, 2020, our balance sheets at October 2, 2021, and January 2, 2021, our statements of stockholders’ equity (deficit) for the nine months ended October 2, 2021, and September 26, 2020, and our statements of cash flows for the nine months ended October 2, 2021, and September 26, 2020. We have condensed or omitted certain notes and other information from the interim condensed consolidated financial statements presented in this report. Therefore, these condensed consolidated interim financial statements should be read in conjunction with the Fiscal 2020 Form 10-K. The results for the three and nine months ended October 2, 2021 are not necessarily indicative of results that may be expected for the full year ending January 1, 2022, or any other interim period. We operate on a 5-4-4 fiscal calendar. Our fiscal year ends on the Saturday closest to December 31 of that fiscal year and may comprise 53 weeks in certain years. Our 2021 fiscal year contains 52 weeks and ends on January 1, 2022. Fiscal 2020 contained 53 weeks and ended on January 2, 2021. Our financial statements are prepared in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”), which requires us to make estimates based on assumptions about current and, for some estimates, future economic and market conditions, which affect reported amounts and related disclosures in our financial statements. Although our current estimates contemplate current and expected future conditions, as applicable, it is reasonably possible that actual conditions could differ from our expectations, which could materially affect our results of operations and financial position. Some of our estimates may be affected by the ongoing novel coronavirus (“COVID-19”) pandemic. The severity, magnitude, and duration, as well as the economic consequences of the COVID-19 pandemic, are uncertain, rapidly changing, and difficult to predict. As a result, our accounting estimates and assumptions may change over time in response to the continuing COVID-19 pandemic. Reclassification of Prior Period Presentation We have reclassified certain costs within the Condensed Consolidated Statements of Operations and Comprehensive Income for the three and nine months ended September 26, 2020, from selling, general and administrative to amortization of deferred gains on real estate. These amounts relate to the amortization of deferred gains from real estate transactions in 2017 and 2018. Refer to Note 9, Leases. Additionally, we reclassified amounts in other comprehensive income from foreign currency translation, net of tax, to other, for the nine months ended October 2, 2021, and three and nine months ended September 26, 2020. We have reclassified certain payables within the Condensed Consolidated Balance Sheets for the year ended January 2, 2021, from other current liabilities to taxes payable. These payables relate to amounts due to various tax authorities. Recently Adopted Accounting Standards Income Taxes. In December 2019, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2019-12, “Income taxes (Topic 740): Simplifying the Accounting for Income Taxes.” This ASU simplifies the accounting for income taxes by removing certain exceptions to the general principles in Accounting Standards Codification (“ASC”) 740 and also clarifies and amends existing guidance to improve consistent application. The amendments in this standard are effective for interim periods and fiscal years beginning after December 15, 2020. Early adoption is permitted. We adopted this standard for the first fiscal quarter of 2021. The adoption of this standard did not have a material impact on the Company’s consolidated financial position, results of operations, or cash flows. Defined Benefit Pension Plan. In August 2018, the FASB issued ASU No. 2018-14, “Compensation-Retirement-Benefits-Defined Benefit Plans-General (Subtopic 715-20).” The amendments in this update modify the disclosure requirements for employers that sponsor defined benefit pension or other post-retirement plans by removing six previously required disclosures and adding two. The ASU also removes the disclosure requirements for the effects of a one-percentage-point change on the assumed health care costs and the effect of this change in rates on service cost, interest cost, and the benefit obligation for postretirement healthcare benefits. We adopted this standard effective for fiscal year 2020. The adoption of this standard did not have a material impact on the Company's consolidated financial position, results of operations, or cash flows. Fair Value Measurement. In August 2018, the FASB issued ASU No. 2018-13, “Fair Value (“FV”) Measurement (Topic 820).” In addition to making certain modifications, the standard removed the requirements to disclose: (i) the amount of and reasons for transfers between Level 1 and Level 2 of the FV hierarchy; (ii) the policy for timing transfers between levels; and (iii) the valuation process for Level 3 FV measurements. The standard requires public entities to disclose: (a) the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 FV measurements held at the end of the reporting period; and (b) the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. For certain unobservable inputs, an entity may disclose other quantitative information in lieu of the weighted average if the entity determines that other quantitative information would be a more reasonable and rational method to reflect the distribution of unobservable inputs used to develop Level 3 FV measurements. The additional disclosure requirements are applied prospectively for the most recent interim or annual period presented in the fiscal year of adoption. All other amendments are applied retrospectively to all periods presented. We adopted this standard effective December 29, 2019, the first day of our 2020 fiscal year. The adoption of this standard did not have a material impact on the Company's consolidated financial position, results of operations, or cash flows. Accounting Standards Effective in Future Periods Credit Impairment Losses. In June 2016, the FASB issued ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326).” This ASU sets forth a current expected credit loss (“CECL”) model which requires the measurement of all expected credit losses for financial instruments or other assets (e.g., trade receivables), held at the reporting date based on historical experience, current conditions, and reasonable supportable forecasts. This replaces the existing incurred loss model, is applicable to the measurement of credit losses on financial assets measured at amortized cost, and applies to some off-balance sheet credit exposures. The standard also requires enhanced disclosures to help financial statement users better understand significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an entity's portfolio. ASU 2019-10 extended the effective date of ASU 2016-13 to interim and annual periods beginning after December 15, 2022, for certain public business entities, including smaller reporting companies. We have not completed our assessment of the standard, but we do not expect the adoption to have a material impact on the Company's consolidated financial position, results of operations, or cash flows.