Significant Accounting Policies (Policies)	12 Months Ended
Significant Accounting Policies (Policies)	Dec. 31, 2018
Accounting Policies [Abstract]
Nature of Business, Policy [Policy Text Block]	Nature of Business The Company operates in three reportable segments; carbon flat products, specialty metals flat products, and tubular and pipe products. The carbon flat products segment and the specialty metals flat products segments are at times consolidated and referred to as the flat products segments. Certain of the flat products segments’ assets and resources are shared by the carbon and specialty metals segments and both segments’ products are stored in the shared facilities and, in some locations, processed on shared equipment. Due to the shared assets and resources, certain of the flat products segment expenses are allocated between the carbon flat products segment and the specialty metals flat products segment based upon an established allocation methodology. Through its carbon flat products segment, the Company sells and distributes large volumes of processed carbon and coated flat-rolled sheet, coil and plate products, and fabricated parts. Through its specialty metals flat products segment, the Company sells and distributes processed aluminum and stainless flat-rolled sheet and coil products, flat bar products and fabricated parts. Through its acquisition of Berlin Metals, LLC (Berlin Metals) on April 2, 2018, the specialty metals flat products segment expanded its product offerings to include differing types of stainless flat-rolled sheet and coil and prime tin mill products. Through its tubular and pipe products segment, which consists of the Chicago Tube and Iron subsidiary (CTI), the Company distributes metal tubing, pipe, bar, valves and fittings and fabricate pressure parts supplied to various industrial markets.
Consolidation, Policy [Policy Text Block]	Principles of Consolidation and Basis of presentation The accompanying consolidated financial statements include the accounts of Olympic Steel, Inc. and its wholly-owned subsidiaries (collectively, the Company or Olympic), after elimination of intercompany accounts and transactions.
Use of Estimates, Policy [Policy Text Block]	Accounting Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States 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.
Concentration Risk, Credit Risk, Policy [Policy Text Block]	Concentration Risks The Company is a major customer of flat-rolled coil and plate and tubular and pipe steel for many of its principal suppliers, but is not dependent on any one supplier. The Company purchased approximately 52%, 53% and 54% of its total steel requirements from its three largest suppliers in 2018, 2017 and 2016, respectively. The Company has a diversified customer and geographic base, which reduces the inherent risk and cyclicality of its business. The concentration of net sales to the Company’s top 20 customers approximated 29%, 27% and 29% of consolidated net sales in 2018, 2017 and 2016, respectively. In addition, the Company’s largest customer accounted for approximately 5%, 4% and 4% of consolidated net sales in 2018, 2017 and 2016, respectively. Sales to industrial machinery and equipment manufacturers and their fabricators accounted for 48%, 51% and 51% of consolidated net sales in 2018, 2017 and 2016, respectively.
Cash and Cash Equivalents, Policy [Policy Text Block]	Cash and Cash Equivalents Cash equivalents consist of short-term highly liquid investments, with a three month or less maturity, which are readily convertible into cash.
Fair Value Measurement, Policy [Policy Text Block]	Fair Market Value Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market for the liability in an orderly transaction between market participants on the measurement date. Valuation techniques must maximize the use of observable inputs and minimize the use of unobservable inputs. To measure fair value, the Company applies a fair value hierarchy that is based on three levels of inputs, of which the first two are considered observable and the last unobservable, as follows: Level 1 – Quoted prices in active markets for identical assets or liabilities. Level 2 – Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 – Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Financial instruments, such as cash and cash equivalents, accounts receivable, accounts payable and the credit facility, are stated at their carrying value, which is a reasonable estimate of fair value. The fair value of marketable securities is based on quoted market prices.
Trade and Other Accounts Receivable, Policy [Policy Text Block]	Accounts Receivable The Company’s allowance for doubtful accounts is maintained at a level considered appropriate based on historical experience and specific customer collection issues that the Company has identified. Estimations are based upon the application of a historical collection rate to the outstanding accounts receivable balance, which remains fairly level from year to year, and judgments about the probable effects of economic conditions on certain customers, which can fluctuate significantly from year to year. The Company cannot guarantee that the rate of future credit losses will be similar to past experience. The Company considers all available information when assessing the adequacy of the allowance for doubtful accounts each quarter.
Inventory, Policy [Policy Text Block]	Inventories Inventories are stated at the lower of its cost or net realizable value. Inventory costs include the costs of the purchased metals, inbound freight, external and internal processing and applicable labor and overhead costs. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal and transportation. Costs of the Company’s carbon and specialty metals flat products segments’ inventories, including flat-rolled sheet, coil and plate products are determined using the specific identification method. Certain of the Company’s tubular and pipe products inventory is stated under the last-in, first -out (LIFO) method. At December 31, 2018 and December 31, 2017, approximately $51.1 million, or 13.9% of consolidated inventory, and $48.1 million, or 17.5% of consolidated inventory, respectively, was reported under the LIFO method of accounting. The cost of the remainder of tubular and pipe product segment’s inventory is determined using a weighted average rolling first -in, first -out (FIFO) method. On the Consolidated Statements of Comprehensive Income, “Cost of materials sold (exclusive of items shown separately below)” consists of the cost of purchased metals, inbound and internal transfer freight, external processing costs, and LIFO income or expense.
Property, Plant and Equipment, Policy [Policy Text Block]	Property and Equipment, and Depreciation Property and equipment are stated at cost. Depreciation is provided using the straight-line method over the estimated useful lives of the assets ranging from two to 30 years. The Company capitalizes the costs of obtaining or developing internal-use software, including directly related payroll costs. The Company amortizes those costs over five years, beginning when the software is ready for its intended use.
Impairment or Disposal of Long-Lived Assets, Including Intangible Assets, Policy [Policy Text Block]	Intangible Assets and Recoverability of Long-lived Assets The Company performs an annual impairment test of indefinite-lived intangible assets in the fourth quarter, or more frequently if changes in circumstances or the occurrence of events indicate potential impairment. Events or changes in circumstances that could trigger an impairment review include significant nonperformance relative to the expected historical or projected future operating results, significant changes in the manner of the use of the acquired assets or the strategy for the overall business or significant negative industry or economic trends. Management uses judgment to determine whether to use a qualitative analysis or a quantitative fair value measurement for each of the Company’s reporting units that carry intangible assets. If a quantitative fair value measurement is used, the fair value of each indefinite-lived intangible asset is compared to its carrying value and an impairment charge is recorded if the carrying value exceeds the fair value. The Company estimates the fair value of indefinite-lived intangible assets using a discounted cash flow methodology. Management’s assumptions used for the calculations are based on historical results, projected financial information and recent economic events. Actual results could differ from these estimates under different assumptions or conditions which could adversely affect the reported value of intangible assets. The Company evaluates the recoverability of long-lived assets and the related estimated remaining lives whenever events or changes in circumstances indicate that the carrying value may not be recoverable. Events or changes in circumstances that could trigger an impairment review include significant underperformance relative to the expected historical or projected future operating results, significant changes in the manner of the use of the acquired assets or the strategy for the overall business or significant negative industry or economic trends. The Company records an impairment or change in useful life whenever events or changes in circumstances indicate that the carrying amount may not be recoverable or the useful life has changed.
Income Tax, Policy [Policy Text Block]	Income Taxes The Company records, as an offset to the estimated effect of temporary differences between the tax basis of assets and liabilities and the reported amounts in its consolidated balance sheets, the tax effect of operating loss and tax credit carryforwards. If the Company determines that it will not be able to fully realize a deferred tax asset, it will record a valuation allowance to reduce such deferred tax asset to its realizable value. The Company recognizes interest accrued related to unrecognized tax benefits in income tax expense. Penalties, if incurred, would be recognized as a component of administrative and general expense.
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition The Company's contracts with customers are comprised of purchase orders with standard terms and conditions. Occasionally the Company may also have longer-term agreements with customers. Substantially all of the contracts with customers require the delivery of metals which represent single performance obligations that are satisfied upon transfer of control of the product to the customer. Transfer of control is assessed based on the use of the product distributed and rights to payment for performance under the contract terms. Transfer of control and revenue recognition for substantially all of the Company’s sales occur upon shipment or delivery of the product, which is when title, ownership and risk of loss pass to the customer and is based on the applicable shipping terms. The shipping terms depend on the customer contract. An invoice for payment is issued at time of shipment and terms are generally net 30 days. The Company has certain fabrication contracts in one business unit for which revenue is recognized over time as performance obligations are achieved. This fabrication business is immaterial to the Company's consolidated results. Sales returns and allowances are treated as reductions to sales and are provided for based on historical experience and current estimates and are immaterial to the consolidated financial statements. Shipping and Handling Fees and Costs Amounts charged to customers for shipping and other transportation services are included in net sales. The distribution expense line on the accompanying Consolidated Statements of Comprehensive Income is entirely comprised of all shipping and other transportation costs incurred by the Company in shipping goods to its customers.
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	Stock-Based Compensation The Company records compensation expense for stock awards issued to employees and directors. For additional information, see Note 11, Equity Plans.
New Accounting Pronouncements, Policy [Policy Text Block]	Impact of Recently Issued Accounting Pronouncements In August, 2018, the Financial Account Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018 - 15, “Intangibles – Goodwill and other – Internal-use software: Customer’s accounting for implementation costs incurred in a cloud computing arrangement that is a service contract”. This ASU aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). Accordingly, this ASU requires an entity (customer) in a hosting arrangement that is a service contract to follow the guidance in Subtopic 350 - 40 to determine which implementation costs to capitalize as an asset related to the service contract and which costs to expense. This ASU also requires the entity (customer) to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement, which includes reasonably certain renewals. For public business entities, this ASU is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years with early adoption permitted. The Company early adopted ASU 2018 - 15 in the third quarter of 2018 and the adoption of this ASU did not materially impact the Company’s consolidated financial statements. In August 2017, the FASB issued ASU No 2017 - 12, “Derivatives and Hedging”. This ASU aligns an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. To meet that objective, this ASU expands and refines hedge accounting for both nonfinancial and financial risk components and align the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. This ASU also makes certain targeted improvements to simplify the application of hedge accounting guidance and ease the administrative burden of hedge documentation requirements and assessing hedge effectiveness. This ASU is the final version of proposed ASU 2016 - 310, “Derivatives and Hedging (Topic 815 ): Targeted Improvements to Accounting for Hedging Activities”, which has been deleted. For public business entities, this ASU is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted in any interim period after issuance of the ASU. All transition requirements and elections should be applied to hedging relationships existing (that is, hedging relationships in which the hedging instrument has not expired, been sold, terminated, or exercised or the entity has not removed the designation of the hedging relationship) on the date of adoption. The effect of adoption should be reflected as of the beginning of the fiscal year of adoption. The adoption of this ASU is not expected to materially impact the Company’s consolidated financial statements. In May 2017, the FASB issued ASU No 2017 - 09, “Compensation – Stock Compensation (Topic 718 )”. This ASU provides clarity and reduces both ( 1 ) diversity in practice and ( 2 ) cost and complexity when applying the guidance in Topic 718, Compensation – Stock Compensation, to a change to the terms or conditions of a share-based payment award. This ASU provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. This ASU is the final version of proposed ASU 2016 - 360, “Compensation—Stock Compensation (Topic 718 )—Scope of Modification Accounting,” which has been deleted. The amendments in this ASU are effective for all entities for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. The amendments in this ASU should be applied prospectively to an award modified on or after the adoption date. The adoption of this ASU did not materially impact the Company’s consolidated financial statements. In February 2016, the FASB issued ASU No. 2016 - 02, “Leases,” which specifies the accounting for leases. The objective is to establish the principles that lessees and lessors shall apply to report useful information to users of financial statements about the amount, timing and uncertainty of cash flows arising from a lease. This ASU introduces the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous guidance. The guidance is effective for annual reporting periods beginning after December 15, 2018 and interim periods within those fiscal years with early adoption permitted. The Company will adopt ASU No. 2016 - 02 as of January 1, 2019. The adoption of the guidance will impact the Company’s Consolidated Balance Sheets by the creation of right to use assets and lease liabilities in the range of $22 million to $27 million. The adoption of this ASU is not expected to have a material impact on the Company’s Statement of Comprehensive Income or on the Statement of Cash Flows. In August 2015, the FASB issued ASU 2015 - 14, “Revenue from Contracts with Customers (Topic 606 ): Deferral of the Effective Date,” which deferred the effective date of ASU 2014 - 09 for all entities by one year. The Company adopted this standard on January 1, 2018. The Company completed the process of evaluating the effect of the adoption and determined there were no material changes required to the reported revenues as a result of the adoption. Substantially all of the revenue arrangements consist of a single performance obligation to transfer goods. Based on the evaluation process and review of the contracts with customers, the timing and amount of revenue recognized based on ASU 2015 - 14 is consistent with the revenue recognition policy under previous guidance. The adoption of this ASU on January 1, 2018 using the modified retrospective approach applied to those contracts which were not completed as of January 1, 2018 did not have a material impact on the Company’s consolidated financial statements. Comparative information has not been restated and continues to be reported under the accounting standard in effect for those periods. The impact of adopting ASU 606 was not material to the Company’s consolidated financial statements as of and for the twelve months ended December 31, 2018. See Note 3, Revenue Recognition.