Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 28, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements include the accounts of BlueLinx Holdings Inc. and its wholly owned subsidiaries (the “Company”). These financial statements have been prepared in accordance with the instructions to Form 10-Q and do not include all of the information and footnotes required by accounting principles generally accepted (“GAAP”) in the United States (“U.S.”) for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. These statements should be read in conjunction with the Consolidated Financial Statements and notes thereto included in the Company’s Annual Report on Form 10-K (the “Annual Report on Form 10-K”) for the year ended December 29, 2018, as filed with the Securities and Exchange Commission on March 13, 2019.
Reclassifications	Certain prior period amounts have been reclassified to conform to the current period's presentation. These reclassifications did not materially impact the Company's operating income (loss) or consolidated net income (loss).
Recently Adopted Accounting Standards and Standards Effective in Future Years	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 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. Lease expenses will continue to be recognized in the consolidated statement of income (loss) 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. Additionally, $1.7 million of deferred gains associated with sale-leaseback transactions was recorded as a cumulative-effect adjustment to accumulated deficit. See Note 9 “Leases” for additional disclosures regarding our lease commitments. Comprehensive Income. In February 2018, the FASB issued ASU No. 2018-02, “Income Statement-Reporting Comprehensive Income (Topic 220).” This standard provides an option to reclassify stranded tax effects within accumulated other comprehensive loss to retained earnings due to the U.S. federal corporate income tax rate change in the Tax Cuts and Jobs Act of 2017. This standard was effective for interim and annual reporting periods beginning after December 15, 2018. We did not exercise the option to make this reclassification. Accounting Standards Effective in Future Years 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. The standard is effective for reporting periods beginning after December 15, 2019. 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. Goodwill. In January 2017, the FASB issued ASU No. 2017-04, “Intangibles—Goodwill and Other (Topic 350).” This ASU is intended to simplify the test for goodwill impairments by removing Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. Under the new ASU, a goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The accounting standard will be effective for reporting periods beginning after December 15, 2019, and early adoption is permitted. We do not expect the adoption of the standard to 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).” Among other modifications, this ASU removes 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 will require 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 should be applied prospectively for the most recent interim or annual period presented in the fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented. The amendments in this standard are effective for fiscal years beginning after December 15, 2019. Early adoption is permitted, and an entity may adopt the removed or modified disclosures and delay the adoption of new disclosures until the effective date. 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.
Revenue Recognition	We recognize revenue when control of promised goods or services is transferred to the Company’s customers in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. Contracts with our customers are generally in the form of standard terms and conditions of sale. From time to time, we may enter into specific contracts with some of our larger customers, which may affect delivery terms. Performance obligations in our contracts generally consist solely of delivery of goods. For all sales channel types, consisting of warehouse, direct, and reload sales, we typically satisfy our performance obligations upon shipment. Our customer payment terms are typical for our industry, and may vary by the type and location of our customer and the products or services offered. The term between invoicing and when payment is due is not deemed to be significant by us. For certain sales channels and/or products, our standard terms of payment may be as early as ten days. In addition, we provide inventory to certain customers through pre-arranged agreements on a consignment basis. Customer consigned inventory is maintained and stored by certain customers; however, ownership and risk of loss remain with us. When the consigned inventory is sold by the customer, we recognize revenue, net of trade allowances. All revenues recognized are net of trade allowances (i.e., rebates), cash discounts and sales returns. Cash discounts and sales returns are estimated using historical experience. Trade allowances are based on the estimated obligations and historical experience. Adjustments to earnings resulting from revisions to estimates on discounts and returns have been insignificant for each of the reported periods. Certain customers may receive cash-based incentives or credits (rebates), which are accounted for as variable consideration. We estimate these amounts based on the expected amount to be provided to customers and reduce revenues recognized. We believe that there will not be significant changes to our estimates of variable consideration. Practical Expedients and Exemptions We generally expense sales commissions when incurred because the amortization period would have been one year or less. These costs are recorded within selling, general, and administrative expense. We have made an accounting policy election to treat any common carrier shipping and handling activities as an expense.
Earnings per Share	We calculate basic loss per share by dividing net loss by the weighted average number of common shares outstanding. We calculate diluted earnings per share by dividing net income by the weighted average number of common shares outstanding plus the dilutive effect of outstanding share-based awards, including restricted stock units, and performance units.