Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 29, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation BlueLinx is a wholesale distributor of building and industrial products in the U.S. Our Consolidated Financial Statements include the accounts of BlueLinx Holdings Inc. and its wholly owned subsidiaries. These financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”). All significant intercompany accounts and transactions have been eliminated. Fiscal years 2018, 2017, and 2016 were each comprised of 52 weeks. Our fiscal year ends on the Saturday closest to December 31 of that fiscal year, and may comprise 53 weeks in certain years. Use of Estimates We are required to make estimates and assumptions when preparing our Consolidated Financial Statements in accordance with U.S. GAAP. These estimates and assumptions affect the amounts reported in our Consolidated Financial Statements and the accompanying notes. Actual results could differ materially from those estimates. Subsequent Events We evaluated subsequent events through the date that our Consolidated Financial Statements were issued. Except as described in Note 19, no matters were identified that required adjustment of the Consolidated Financial Statements or additional disclosure. Recent Accounting Standards - Recently Issued 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 for leases. 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. Expenses are recognized in the consolidated statement of income in a manner similar to current 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 fiscal 2019 year, using a prospective transition 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 are finalizing our evaluation of the impacts that the adoption of this accounting guidance will have on the consolidated financial statements, and estimate approximately $60 - $65 million of additional right-of-use assets and liabilities will be recognized in our consolidated balance sheet upon adoption. Additionally, approximately $1.7 million of deferred gains associated with sale-leaseback transactions will be recorded as a cumulative-effect adjustment to accumulated deficit. Goodwill. In January 2017, the FASB issued ASU No. 2017-04, “Intangibles-Goodwill and Other (Topic 350).” This standard 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 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 and cash flows. 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 income (loss) (“AOCI”) 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 is effective for interim and annual reporting periods beginning after December 15, 2018, and early adoption is permitted. We have not completed our assessment, but the adoption of the standard may impact tax amounts stranded in AOCI related to our pension plans. We adopted this standard effective December 30, 2018, the first day of our fiscal 2019 year. 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 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: (i) 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 (ii) 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 ending after December 15, 2019. Early adoption is permitted, and an entity may early 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 and 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 postretirement plans by removing six previously required disclosures and adding two. The amendments also clarify certain 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 and cash flows. Recent Accounting Standards - Recently Adopted Revenue from Contracts with Customers. In 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASC 606”) that superseded existing revenue recognition guidance. Under this ASU and subsequently issued amendments, revenue is recognized at the time a good or service is transferred to a customer for the amount of consideration received. The standard was effective for the first interim period within annual periods beginning after December 15, 2017, with early adoption permitted for annual periods beginning after December 15, 2016. Entities were permitted to adopt the standard using a “full retrospective” approach (retrospectively to each prior reporting period presented) or a “modified retrospective” approach (reporting the cumulative effect as of the date of adoption). On December 31, 2017, the first day of our fiscal 2018 year, we adopted ASC 606 using the modified retrospective method applied to those contracts which were not completed as of that date. Results for reporting periods beginning after the first day of fiscal 2018 are presented under ASC 606, while prior period amounts are not adjusted and continue to be reported in accordance with our historic accounting under the previous accounting standard, ASC 605. There was no adjustment due to the cumulative impact of adopting ASC 606 (See Note 3). Revenue Recognition We recognize revenue when control of the promised goods or services is transferred to the Company’s customers in an amount that reflects the consideration we expected to be entitled to in exchange for those goods or services. The timing of revenue recognition largely is dependent on shipping terms. Revenue is recorded at the time of shipment for terms designated free on board (“FOB”) shipping point. For sales transactions designated FOB destination, revenue is recorded when the product is delivered to the customer’s delivery site. 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 remains with us. When the consigned inventory is sold by the customer, we recognize revenue on a gross basis. All revenues recognized are net of trade allowances, 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. Accounts Receivable Accounts receivable are stated at net realizable value, do not bear interest, and consist of amounts owed for orders shipped to customers. Management establishes an overall credit policy for sales to customers. The allowance for doubtful accounts is determined based on a number of factors including specific customer account reviews, historical loss experience, current economic trends, and the creditworthiness of significant customers based on ongoing credit evaluations. Inventory Valuation The cost of all inventories is determined by the moving average cost method. We have included all material charges directly or indirectly incurred in bringing inventory to its existing condition and location. We evaluate our inventory value at the end of each quarter to ensure that inventory, when viewed by category, is carried at the lower of cost and net realizable value, which also considers items that may be damaged, excess, and obsolete inventory. Consideration Received from Vendors and Paid to Customers Each year, we enter into agreements with many of our vendors providing for inventory purchase rebates, generally based on achievement of specified volume purchasing levels. We also receive rebates related to price protection and various marketing allowances that are common industry practice. We accrue for the receipt of vendor rebates based on purchases, and also reduce inventory to reflect the net acquisition cost (purchase price less expected purchase rebates). In addition, we enter into agreements with many of our customers to offer customer rebates, generally based on achievement of specified sales levels and various marketing allowances that are common industry practice. We accrue for the payment of customer rebates based on sales to the customer, and also reduce sales to reflect the net sales (sales price less expected customer rebates). Adjustments to earnings resulting from revisions to rebate estimates have been immaterial. Shipping and Handling Shipping and handling costs included in “Selling, general, and administrative” expenses were $121.8 million, $83.1 million, and $89.0 million for fiscal 2018, fiscal 2017, and fiscal 2016, respectively. Property and Equipment Property and equipment are recorded at cost. Lease obligations for which we assume or retain substantially all the property rights and risks of ownership are capitalized. Amortization of assets recorded under capital leases is included in “Depreciation and amortization” expense. Replacements of major units of property are capitalized and the replaced properties are retired. Replacements of minor components of property and repair and maintenance costs are charged to expense as incurred. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets. Upon retirement or disposition of assets, cost and accumulated depreciation are removed from the related accounts and any gain or loss is included in income. Income Taxes We account for deferred income taxes using the liability method. Accordingly, we recognize deferred tax assets and liabilities based on the tax effects of temporary differences between the financial statement and tax bases of assets and liabilities, as measured by current enacted tax rates. All deferred tax assets and liabilities are classified as noncurrent in our consolidated balance sheet. A valuation allowance is recorded to reduce deferred tax assets when necessary. For additional information about our income taxes, see Note 8, “Income Taxes.” Insurance and Self-Insurance For fiscal 2018, 2017, and 2016, the Company purchased an insurance policy for its non-union and certain unionized employee health benefits, and was fully insured for this obligation. Health benefits for some unionized employees for fiscal 2018, 2017, and 2016 were paid directly to a union trust, depending upon the union-negotiated benefit arrangement. For fiscal 2018, 2017, and 2016, the Company was self-insured, up to certain limits, for most workers’ compensation losses, general liability, and automotive liability losses, all subject to varying “per occurrence” retentions or deductible limits. The Company provides for estimated costs to settle both known claims and claims incurred but not yet reported. Liabilities associated with these claims are estimated, in part, by considering the frequency and severity of historical claims, both specific to us, as well as industry-wide loss experience and other actuarial assumptions. We determine our insurance obligations with the assistance of actuarial firms. Since there are many estimates and assumptions involved in recording insurance liabilities and in the case of workers’ compensation, a significant period of time elapses before the ultimate resolution of claims, differences between actual future events and prior estimates and assumptions could result in adjustments to these liabilities.