Basis of Presentation and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 28, 2020
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	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”). Our independent registered public accounting firm has not audited the accompanying interim financial statements. We derived the condensed consolidated balance sheet at March 28, 2020, from the audited consolidated financial statements included in our Annual Report on Form 10-K for the fiscal year ended December 28, 2019 (the “Fiscal 2019 Form 10-K”), as filed with the Securities and Exchange Commission on March 11, 2020. 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 loss for the three months ended March 28, 2020, and March 30, 2019, our balance sheets at March 28, 2020 and December 28, 2019, our statements of cash flows for the three months ended March 28, 2020 and March 30, 2019, and our statements of stockholders’ deficit for the three months ended March 28, 2020 and March 30, 2019. 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 2019 Form 10-K. In addition, certain prior period amounts have been reclassified to conform to the current period's presentation. These reclassifications did not materially impact operating income or consolidated net loss. The results for the three months ended March 28, 2020, are not necessarily indicative of results that may be expected for the full year ending January 2, 2021, 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 2020 fiscal year contains 53 weeks and ends on January 2, 2021. Fiscal 2019 contained 52 weeks and ended on December 28, 2019. 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 COVID-19. On April 13, 2018, we completed the acquisition of Cedar Creek Holdings, Inc. (“Cedar Creek”). The accounting for the Cedar Creek acquisition was finalized on December 29, 2018 and is included in the consolidated financial information presented herein. Reclassification of Prior Year Presentation An adjustment has been made to the Condensed Consolidated Statements of Cash Flows for the three months ended March 28, 2020, and March 30, 2019, to include outstanding payments as part of the change in accounts payable within cash flows from operating activities. In previous periods, this change was included within cash flows from financing activities. We believe this classification is a preferable way to present our cash flows as outstanding payments are included in accounts payable within our Condensed Consolidated Balance Sheet. Recently Adopted Accounting Standards Leases. In 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, “Leases (Topic 842).” Topic 842 establishes a new lease accounting model. The most significant changes include the clarification of the definition of a lease, the requirement for lessees to recognize for all leases a right-of-use asset and a corresponding lease liability in the consolidated balance sheet, and additional quantitative and qualitative disclosures which are designed to give financial statement users information on the amount, timing, and uncertainty of cash flows arising from leases. Expenses are recognized in the consolidated statement of income in a manner similar to prior accounting guidance. Lessor accounting under the new standard is substantially unchanged. We adopted this standard, and all related amendments thereto, effective December 30, 2018, the first day of our 2019 fiscal year, using a modified retrospective approach, which applies the provisions of the new guidance at the effective date without adjusting the comparative periods presented. We have elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allows us to carry forward the historical accounting relating to lease identification and classification for existing leases upon adoption. We have made an accounting policy election to keep leases with an initial term of 12 months or less off of the consolidated balance sheet. We implemented internal controls and a lease accounting information system to enable the preparation of financial information required by the new standard. The adoption of Topic 842 had a material impact on our condensed consolidated balance sheets but did not have a material impact on our condensed consolidated statements of operations and comprehensive loss. The most significant impact was the recognition of right-of-use assets and lease liabilities of $57.5 million on the condensed consolidated balance sheet as of the adoption date. Additionally, $1.7 million of deferred gains associated with sale-leaseback transactions was recorded as a cumulative-effect adjustment to accumulated deficit. 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 22, 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. 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 amendments also clarify certain other disclosure requirements. The amendments in this standard are effective for fiscal years ending after December 15, 2020. Early adoption is permitted. 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. Income Taxes. In December 2019, the FASB issued 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 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 are currently assessing the impact of the new guidance, but do not expect the adoption to have a material impact on the Company’s consolidated financial position, results of operations, or cash flows.