Cover [Abstract] Document Type Document Quarterly Report Document Period End Date Document Transition Report Securities Act File Number Entity Registrant Name Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Address, Address Line One Entity Address, City or Town Entity Address, State or Province Entity Address, Postal Zip Code City Area Code Local Phone Number Title of 12(b) Security Trading Symbol Security Exchange Name Entity Current Reporting Status Entity Interactive Data Current Entity Filer Category Entity Small Business Entity Emerging Growth Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Central Index Key Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Period Focus Amendment Flag CONSOLIDATED BALANCE SHEETS Statement [Table] Related and Nonrelated Parties [Axis] Related and Nonrelated Parties [Domain] Nonrelated Party [Member] Unrelated parties Related Party [Member] Related parties Statement [Line Items] Statement Assets [Abstract] Assets Assets, Current [Abstract] Current assets Cash and Cash Equivalents, at Carrying Value Cash and equivalents Accounts Receivable, after Allowance for Credit Loss, Current Accounts receivable Inventory, Net Inventories Total inventories Other Assets, Current Other current assets Assets, Current Total current assets Property, Plant and Equipment, Net Property, plant and equipment, net Intangible Assets, Net (Excluding Goodwill) Intangible assets, net Goodwill Goodwill Other Assets, Noncurrent Other assets Assets Total assets Total Assets Liabilities and Equity [Abstract] Liabilities and Equity Liabilities, Current [Abstract] Current liabilities Accounts Payable, Current Accounts payable Accrued Income Taxes, Current Income taxes payable Employee-related Liabilities, Current Accrued payroll and benefits Accrued Liabilities, Current Accrued expenses Long-Term Debt, Current Maturities Current maturities of long-term debt Liabilities, Current Total current liabilities Long-Term Debt, Excluding Current Maturities Long-term debt Deferred Income Tax Liabilities, Net Deferred income taxes Other Liabilities, Noncurrent Other liabilities Liabilities Total liabilities Commitments and Contingencies. Commitments and contingencies Redeemable Noncontrolling Interest, Equity, Carrying Amount Redeemable noncontrolling interests Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Equity Common Stock, Value, Issued Common stock voting, $0.0025 par value; 900,000,000 shares authorized; 268,694,947 and 268,644,427 shares issued; and 143,610,058 and 144,940,102 shares outstanding, as of June 30, 2026 and December 31, 2025, respectively Treasury Stock, Common, Value Treasury stock, at cost; 125,084,889 and 123,704,325 shares, as of June 30, 2026 and December 31, 2025, respectively Additional Paid in Capital, Common Stock Additional paid-in capital Retained Earnings (Accumulated Deficit) Retained earnings Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive income (loss) Equity, Attributable to Parent Total Steel Dynamics, Inc. equity Equity, Attributable to Noncontrolling Interest Noncontrolling interests Equity, Including Portion Attributable to Noncontrolling Interest Balances Balances Total equity Liabilities and Equity Total liabilities and equity Common Stock, Par or Stated Value Per Share Common stock voting, par value (in dollars per share) Common Stock, Shares Authorized Common stock voting, shares authorized (in shares) Common Stock, Shares, Issued Common stock voting, shares issued (in shares) Common Stock, Shares, Outstanding Common stock voting, shares outstanding (in shares) Treasury Stock, Common, Shares Treasury stock, shares (in shares) CONSOLIDATED STATEMENTS OF INCOME Revenue from Contract with Customer, Excluding Assessed Tax Total net sales Net sales Cost of Goods and Services Sold Costs of goods sold Gross Profit Gross profit Selling, General and Administrative Expense Selling, general and administrative expenses Other Labor-related Expenses Profit sharing Amortization of Intangible Assets Amortization of intangible assets Operating Income (Loss) Operating income (loss) Operating income Interest Expense, Nonoperating Interest expense, net of capitalized interest Other Nonoperating Income (Expense) Other income, net Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income before income taxes Income before income taxes Income Tax Expense (Benefit) Income tax expense Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income Net income Net income (loss) Net Income (Loss) Attributable to Noncontrolling Interest Net loss (income) attributable to noncontrolling interests Net income attributable to Steel Dynamics, Inc. Earnings Per Share, Basic Basic earnings per share attributable to Steel Dynamics, Inc. stockholders (in dollars per share) Basic (in dollars per share) Weighted Average Number of Shares Outstanding, Basic Basic earnings per share (in shares) Weighted average common shares outstanding (in shares) Earnings Per Share, Diluted Diluted earnings per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share) Diluted (in dollars per share) Weighted Average Number of Shares Outstanding, Diluted Weighted average common shares and share equivalents outstanding (in shares) Diluted earnings per share (in shares) Common Stock, Dividends, Per Share, Declared Dividends declared per share (in dollars per share) CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Other comprehensive income - net unrealized gain on cash flow hedging derivatives, net of income tax expense of $1,305 and $379 for the three months ended, and $1,223 and $379 for the six months ended June 30, 2026 and 2025, respectively. Other comprehensive loss, net of tax Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive loss (income) attributable to noncontrolling interests Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income attributable to Steel Dynamics, Inc. Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax Net of income tax expense related to net unrealized gain on cash flow hedging derivatives CONSOLIDATED STATEMENTS OF CASH FLOWS Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Depreciation, Depletion and Amortization Depreciation and amortization Share-Based Payment Arrangement, Noncash Expense Equity-based compensation The noncash component of income tax expense for the period representing the increase (decrease) in the entity's deferred tax assets and liabilities pertaining to continuing operations. Deferred Income Tax Noncash Expense (Benefit) Deferred income taxes Other Operating Activities, Cash Flow Statement Other adjustments Increase (Decrease) in Operating Capital [Abstract] Changes in certain assets and liabilities: Increase (Decrease) in Accounts Receivable Accounts receivable Increase (Decrease) in Inventories Inventories Increase (Decrease) in Other Operating Assets Other assets Increase (Decrease) in Accounts Payable Accounts payable Increase (Decrease) in Income Taxes Payable, Net of Income Taxes Receivable Income taxes receivable/payable Increase (Decrease) in Accrued Liabilities Accrued expenses Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Investing activities: Payments to Acquire Property, Plant, and Equipment Purchases of property, plant and equipment Payments to Acquire Short-Term Investments Purchases of short-term investments Proceeds from Maturities, Prepayments and Calls of Short-Term Investments Proceeds from maturities of short-term investments Payments for (Proceeds from) Other Investing Activities Other investing activities Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Financing activities: Proceeds from Issuance of Debt Issuance of current and long-term debt Repayments of Debt Repayment of current and long-term debt Payments of Ordinary Dividends, Common Stock Dividends paid Payments for Repurchase of Common Stock Purchases of treasury stock Proceeds from (Payments for) Other Financing Activities Other financing activities Net Cash Provided by (Used in) Financing Activities Net cash used in by financing activities Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Increase (decrease) in cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Cash, cash equivalents, and restricted cash at end of period Cash, cash equivalents, and restricted cash at beginning of period Supplemental Cash Flow Information [Abstract] Supplemental disclosure information: Interest Paid, Excluding Capitalized Interest, Operating Activities Cash paid for interest Income Taxes Paid, Net Cash paid for income taxes, net Description of the Business and Significant Accounting Policies Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Description of the Business and Significant Accounting Policies Business Combinations The entire disclosure for equity method investments and joint ventures. Equity method investments are investments that give the investor the ability to exercise significant influence over the operating and financial policies of an investee. Joint ventures are entities owned and operated by a small group of businesses as a separate and specific business or project for the mutual benefit of the members of the group. Business Combinations And Equity Method Investments [Text Block] Business Combinations Earnings Per Share Earnings Per Share [Text Block] Earnings Per Share Inventories Inventory Disclosure [Text Block] Inventories Changes in Equity Equity [Text Block] Changes in Equity Fair Value Measurements Fair Value Disclosures [Text Block] Fair Value Measurements Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Segment Information Segment Reporting Disclosure [Text Block] Segment Information Consolidation, Policy [Policy Text Block] Principles of Consolidation Use of Estimates, Policy [Policy Text Block] Use of Estimates Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Cash, Cash Equivalents, and Restricted Cash Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Goodwill Credit Loss, Financial Instrument [Policy Text Block] Credit Losses Derivatives, Policy [Policy Text Block] Derivative Financial Instruments New Accounting Pronouncements, Policy [Policy Text Block] Recently Issued Not Yet Adopted Accounting Pronouncements Schedule of Goodwill [Table Text Block] Schedule of Goodwill Business Combination, Pro Forma Information [Table Text Block] Schedule of pro forma information Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Reconciliation of Basic and Diluted Earnings Per Share Schedule of Inventory, Current [Table Text Block] Schedule of Inventories Schedule of Stockholders Equity [Table Text Block] Schedule of Stockholders' Equity Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Operating Segment Results Schedule of Segment Reporting Information, by Segment [Table] Consolidated Entities [Axis] Consolidated Entities [Domain] Subsidiaries [Member] Subsidiaries Represents the information pertaining to the Steel Dynamics, Inc. Biocarbon Solutions (SDI Biocarbon Solutions). Steel Dynamics, Inc. Biocarbon Solutions [Member] SDI Biocarbon Solutions Represents the information pertaining to the United Steel Supply, LLC. United Steel Supply, LLC United Steel Supply, LLC Represents information pertaining to Mesabi Nugget. Mesabi Nugget Mesabi Nugget Represents the information pertaining to Unity Aluminum, Inc. Unity Aluminum, Inc Unity Aluminum, Inc Segments [Axis] Segments [Domain] Steel Segment Operations include the entity's Flat Roll Division, The Techs galvanizing lines, Structural and Rail Division, Engineered Bar Products Division, Roanoke Bar Division, Steel of West Virginia (SWVA). Steel Operations Steel Operations Aluminum operations includes the flat rolled aluminum mill and two satellite recycled aluminum slab centers. Aluminum Operations Aluminum Operations Geographical [Axis] Geographical [Domain] MEXICO Mexico MISSISSIPPI Mississippi Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Domain] Construction in Progress [Member] Construction in Progress Segment Reporting Information [Line Items] Segment Reporting Information Segment Reporting Information, Additional Information [Abstract] Segment Reporting Information Number of Reportable Segments Number of reportable segments The number of satellite recycled aluminum slab centers in aluminum operations. Number Of Satellite Recycled Aluminum Slab Centers Number of Satellite Recycled Aluminum Slab Centers Subsidiary or Equity Method Investee, Cumulative Percentage Ownership after All Transactions Ownership percentage Accounting Standards Update and Change in Accounting Principle [Table] Restricted Cash and Cash Equivalents Restricted Cash and Cash Equivalents Restricted Cash and Cash Equivalents, Statement of Financial Position [Extensible Enumeration] Restricted Cash and Cash Equivalents, Asset, Statement of Financial Position [Extensible List] Goodwill [Table] Consists solely of OmniSource Corporation (OmniSource), and includes both ferrous and nonferrous processing, transportation, marketing, brokerage, and consulting services. Metals Recycling Operations Metals Recycling Operations Steel Fabrication Segment Operations represent the entity's New Millennium Building Systems' plants located throughout the United States. Steel Fabrication Operations Steel Fabrication Operations