Cover Abstract Statement [Table] Statement [Line Items] 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 UNAUDITED CONSOLIDATED STATEMENT OF INCOME Revenue from Contract with Customer, Excluding Assessed Tax Revenues Net sales Costs and Expenses [Abstract] Costs and expenses: Cost of Goods and Service, Excluding Depreciation, Depletion, and Amortization Cost of sales (exclusive of depreciation and amortization shown below) Selling, General and Administrative Expense Warehouse, delivery, selling, general and administrative Depreciation, Depletion and Amortization Depreciation and amortization Depreciation and amortization Costs and Expenses Total costs and expenses Operating Income (Loss) Operating income Nonoperating Income (Expense) [Abstract] Other (income) expense: Interest Expense, Nonoperating Interest expense Other Nonoperating Income (Expense) Other income, net Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income before income taxes Income Tax Expense (Benefit) Income tax provision Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income Net income Net Income (Loss) Attributable to Noncontrolling Interest Less: net income - noncontrolling interests Net income - Reliance EARNINGS PER SHARE Earnings per share: Earnings Per Share, Basic Basic (in dollars per share) Earnings per share - basic (in dollars per share) Earnings Per Share, Diluted Diluted (in dollars per share) Earnings per share - diluted (in dollars per share) Weighted Average Number of Shares Outstanding, Basic [Abstract] Weighted average shares outstanding: Weighted Average Number of Shares Outstanding, Basic Weighted average shares outstanding (in shares) Basic (in shares) Weighted Average Number of Shares Outstanding, Diluted Diluted (in shares) Weighted average diluted shares outstanding (in shares) UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Other Comprehensive Income (Loss), Net of Tax [Abstract] Other comprehensive income (loss): Other comprehensive income (loss): Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Foreign currency translation Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Pension and postretirement benefit plan adjustments, net of tax Other Comprehensive Income (Loss), Net of Tax Total other comprehensive income (loss) Other comprehensive (loss) income 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 income Less: comprehensive income - noncontrolling interests Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income - Reliance UNAUDITED CONSOLIDATED BALANCE SHEETS Assets [Abstract] Assets Assets, Current [Abstract] Current assets: Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents Accounts Receivable, after Allowance for Credit Loss, Current Accounts receivable, less allowance for credit losses of $22.3 and $22.1 Inventory, Net Inventories Prepaid Expense and Other Assets, Current Prepaid expenses and other current assets Income Taxes Receivable, Current Income taxes receivable Assets, Current Total current assets Property, Plant and Equipment, Net. Property, plant and equipment, net Property, plant and equipment, net Operating Lease, Right-of-Use Asset Operating lease right-of-use assets Goodwill. Balance as of the end of the period Balance as of the beginning of the period Goodwill Intangible Assets, Net (Excluding Goodwill) Ending Balance Beginning Balance Intangible assets, net Cash Surrender Value of Life Insurance Cash surrender value of life insurance policies, net Other Assets, Noncurrent Other long-term assets Assets Total assets Liabilities and Equity [Abstract] Liabilities and Equity Liabilities, Current [Abstract] Current liabilities: Accounts Payable, Current Accounts payable Accrued Liabilities, Current Accrued expenses Employee-related Liabilities, Current Accrued compensation and retirement benefits Accrued Insurance, Current Accrued insurance costs Long-Term Debt, Current Maturities Less: amounts due within one year Current maturities of long-term debt Operating Lease, Liability, Current Current maturities of operating lease liabilities Accrued Income Taxes, Current Income taxes payable Liabilities, Current Total current liabilities Long-Term Debt, Excluding Current Maturities Long-term debt Total long-term debt Operating Lease, Liability, Noncurrent Operating lease liabilities Liability, Defined Benefit Plan, Noncurrent Long-term retirement benefits Other Liabilities, Noncurrent Other long-term liabilities Deferred Income Tax Liabilities, Net Deferred income taxes Liabilities Total liabilities Commitments and Contingencies Commitments and contingencies Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Equity: Preferred Stock, Value, Issued Preferred stock, $0.001 par value: 5,000 shares authorized; none issued or outstanding Common Stocks, Including Additional Paid in Capital Common stock and additional paid-in capital, $0.001 par value and 200,000 shares authorized Issued and outstanding shares-51,053 and 51,735 Retained Earnings (Accumulated Deficit) Retained earnings Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive loss Equity, Attributable to Parent Total Reliance stockholders' equity Equity, Attributable to Noncontrolling Interest Noncontrolling interests Equity, Including Portion Attributable to Noncontrolling Interest Balance Balance Total equity Liabilities and Equity Total liabilities and equity Accounts Receivable, Allowance for Credit Loss, Current Accounts receivable, allowance for credit losses Preferred Stock, Par or Stated Value Per Share Preferred stock, par value (in dollars per share) Preferred Stock, Shares Authorized Preferred stock, Authorized shares Preferred Stock, Shares Issued Preferred stock, issued shares Preferred Stock, Shares Outstanding Preferred stock, outstanding shares Common Stock, Par or Stated Value Per Share Common stock, par value (in dollars per share) Common Stock, Shares Authorized Common stock, Authorized shares Common Stock, Shares, Issued Common stock, Issued shares Common Stock, Shares, Outstanding Common stock, outstanding shares UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS Net Cash Provided by (Used in) Operating Activities [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: Share-Based Payment Arrangement, Noncash Expense Stock-based compensation Other Noncash Income (Expense) Other Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Accounts Receivable Accounts receivable Increase (Decrease) in Inventories Inventories Increase (Decrease) in Prepaid Expense and Other Assets Prepaid expenses and other assets Increase (Decrease) in Accounts Payable and Accrued Liabilities Accounts payable and other liabilities Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] Investing activities: Payments to Acquire Businesses, Net of Cash Acquired Acquisitions Payments to Acquire Property, Plant, and Equipment Purchases of property, plant and equipment Proceeds from Sale of Property, Plant, and Equipment Proceeds from sales of property, plant and equipment Payments for (Proceeds from) Other Investing Activities Other Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Financing activities: Proceeds from Issuance of Long-Term Debt Proceeds from long-term debt borrowings Repayments of Long-Term Debt Principal payments on long-term debt Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity and dividend equivalents. Payments of Ordinary Dividends, Common Stock And Dividend Equivalents Cash dividends and dividend equivalents Payments for Repurchase of Common Stock Share repurchases Payment, Tax Withholding, Share-Based Payment Arrangement Taxes paid on net-settled restricted stock units Amount of excise tax payments on share purchased under share repurchase plan. Includes, but is not limited to, repurchase of stock and unit of ownership. Payments For Share Repurchase Program Excise Tax Excise tax on repurchase of common shares Proceeds from (Payments for) Other Financing Activities Other Net Cash Provided by (Used in) Financing Activities Net cash used in financing activities Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations Effect of exchange rate changes on cash and cash equivalents Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Increase (decrease) in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Cash and cash equivalents, ending balance Cash and cash equivalents, beginning balance Supplemental Cash Flow Information [Abstract] Supplemental cash flow information: Interest Paid, Excluding Capitalized Interest, Operating Activities Interest paid Income Taxes Paid, Net Income taxes paid, net UNAUDITED CONSOLIDATED STATEMENTS OF EQUITY Equity Components [Axis] Equity Component [Domain] Parent [Member] Reliance Stockholders' Common Stock Including Additional Paid in Capital [Member] Common Stock and Additional Paid in Capital Retained Earnings [Member] Retained Earnings AOCI Attributable to Parent [Member] Accumulated Other Comprehensive loss Noncontrolling Interest [Member] Non-controlling Interests Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity Schedule of accumulated other comprehensive loss Dividends, Common Stock, Cash Cash dividends Amount of paid and unpaid common stock dividend equivalents declared with the form of settlement in cash. Dividend Equivalents Common Stock Cash Dividend equivalents paid on vested restricted stock units Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Noncontrolling interest purchased Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Dividends paid APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Stock-based compensation Share-Based Payment Arrangement, Decrease for Tax Withholding Obligation Taxes paid on net-settled restricted stock units Shares withheld related to share settlements Stock Repurchased and Retired During Period, Value Share repurchases Value of shares repurchased Share Repurchase Program, Excise Tax Excise tax on repurchase of common shares Common Stock, Dividends, Per Share, Declared Common stock quarterly dividend per share (in dollars per share) Cash dividends declared per common share (in dollars per share) SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES REVENUES Revenue from Contract with Customer [Text Block] REVENUES PROPERTY, PLANT AND EQUIPMENT, NET Property, Plant and Equipment Disclosure [Text Block] PROPERTY, PLANT AND EQUIPMENT, NET GOODWILL Goodwill Disclosure [Text Block] GOODWILL INTANGIBLE ASSETS, NET Intangible Assets Disclosure [Text Block] INTANGIBLES ASSETS, NET DEBT Debt Disclosure [Text Block] DEBT LEASES Lessee, Operating Leases [Text Block] LEASES INCOME TAXES Income Tax Disclosure [Text Block] INCOME TAXES EQUITY Equity [Text Block] EQUITY Earnings Per Share [Text Block] EARNINGS PER SHARE COMMITMENTS AND CONTINGENCIES. Commitments and Contingencies Disclosure [Text Block] COMMITMENTS AND CONTINGENCIES SEGMENT INFORMATION Schedule of Segment Reporting Information, by Segment [Table] Segment Reporting Disclosure [Text Block] SEGMENT INFORMATION Consolidation, Policy [Policy Text Block] Principles of Consolidation Inventory, Policy [Policy Text Block] Inventories Goodwill and Intangible Assets, Intangible Assets, Indefinite-Lived, Policy [Policy Text Block] Goodwill and Other Indefinite-Lived Intangible Assets New Accounting Pronouncements, Policy [Policy Text Block] Recently Issued Accounting Standards Disaggregation of Revenue [Table Text Block] Schedule of disaggregation of revenue Property, Plant and Equipment [Table Text Block] Schedule of property, plant and equipment, net Schedule of Goodwill [Table Text Block] Schedule of changes in the carrying amount of goodwill Schedule of Intangible Assets and Goodwill [Table Text Block] Summary of intangible assets, net Tabular disclosure of changes in carrying amount of intangible assets, net. Schedule of Intangible Assets Roll Forward [Table Text Block] Schedule of carrying amount of intangible assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Summary of estimated aggregate amortization expense Schedule of Debt [Table Text Block] Summary of debt Represents the lessee operating lease supplemental cash flow and other lease information. Lessee Operating Lease Supplemental Cash Flow And Other Lease Information Table Text Block Schedule of supplemental cash flow and other lease information Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] Summary of the status of the Company's restricted stock units and changes during the period Schedule of Repurchase Agreements [Table Text Block] Schedule of share repurchase activity Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Schedule of accumulated other comprehensive loss Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Computation of basic and diluted earnings per share Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of segment revenue, net income, significant expenses, and other quantitative information Disaggregation of Revenue [Table] Product and Service [Axis] Product and Service [Domain] Represents carbon steel, a product that is sold by the entity. Carbon steel Carbon steel Represents aluminum, a product that is sold by the entity. Aluminum Aluminum Represents stainless steel, a product that is sold by the entity. Stainless steel Stainless steel Represents alloy steel, a product that is sold by the entity. Alloy Alloy Represents the toll processing service that is provided by the entity. Toll processing and logistics Toll processing and logistics Represents copper and brass, a product that is sold by the entity. Copper and brass Copper and brass Represents the other products and eliminations. Other and eliminations Miscellaneous and eliminations Miscellaneous Disaggregation of Revenue [Line Items] Revenue Disaggregation Property, Plant and Equipment [Table] Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Domain] Land [Member] Land Building [Member] Buildings Machinery and Equipment [Member] Machinery and equipment Construction in Progress [Member] Construction in progress Property, Plant and Equipment [Line Items] Property, Plant and Equipment Property, Plant and Equipment, Gross Property, plant and equipment, gross Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Less: accumulated depreciation Capital Expenditures Incurred but Not yet Paid Capital expenditures included in accounts payable/accrued expense Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Line Items] Goodwill Goodwill [Roll Forward] Change in the carrying amount of goodwill Goodwill, Other Increase (Decrease) Other Goodwill, Foreign Currency Translation Gain (Loss) Foreign currency translation Goodwill, Impaired, Accumulated Impairment Loss Accumulated impairment losses Disclosure of the carrying value of amortizable finite-lived intangible assets, including the disclosure of the carrying value of indefinite-lived intangible assets not subject to amortization, excluding goodwill, in total and by major class. Schedule of Finite Lived and Indefinite Lived Intangible Assets by Major Class [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Customer Lists [Member] Customer lists/relationships Order or Production Backlog [Member] Backlog of orders Other Intangible Assets [Member] Other Indefinite-Lived Intangible Assets [Axis] Indefinite-Lived Intangible Assets, Major Class Name [Domain] Trade Names [Member] Trade names Finite Lived and Indefinite Lived Intangible Assets [Line Items] Intangible assets Finite-Lived Intangible Assets, Net [Abstract] Intangible assets subject to amortization: Finite-Lived Intangible Asset, Useful Life Weighted average amortizable life in years Finite-Lived Intangible Assets, Gross Intangible assets subject to amortization, Gross Carrying Amount Finite-Lived Intangible Assets, Accumulated Amortization Intangible assets subject to amortization, Accumulated Amortization Indefinite-Lived Intangible Assets (Excluding Goodwill) [Abstract] Intangible assets not subject to amortization: Indefinite-Lived Intangible Assets (Excluding Goodwill) Intangible assets not subject to amortization, Gross Carrying Amount Intangible Assets, Net [Abstract] Intangible assets Intangible Assets, Gross (Excluding Goodwill) Intangible assets, Gross Carrying Amount Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Summary of estimated aggregate amortization expense for each of the succeeding five years and thereafter Finite-Lived Intangible Asset, Expected Amortization, Remainder of Fiscal Year 2026 - remaining Finite-Lived Intangible Asset, Expected Amortization, Year One 2027 Finite-Lived Intangible Asset, Expected Amortization, Year Two 2028 Finite-Lived Intangible Asset, Expected Amortization, Year Three 2029 Finite-Lived Intangible Asset, Expected Amortization, Year Four 2030 Definition: Amount of amortization for asset, excluding financial asset and goodwill, lacking physical substance with finite life expected to be recognized after fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Finite Lived Intangible Assets Amortization Expense After Year Four Thereafter Finite-Lived Intangible Assets, Net Total Amount of other increases (decreases) an asset, excluding financial assets and goodwill, lacking physical substance. Intangible Assets (Excluding Goodwill), Other Other Amortization of Intangible Assets Amortization expense Amount of foreign currency translation gain (loss) which increases (decreases) an asset, excluding financial assets and goodwill, lacking physical substance. Intangible Assets (Excluding Goodwill), Foreign Currency Translation Gain (Loss) Foreign currency translation Schedule of Long-Term Debt Instruments [Table] Debt Instrument [Axis] Debt Instrument, Name [Domain] A contractual arrangement to borrow and repay an amount under an unsecured revolving credit facility due in September 2029. Unsecured Revolving Credit Facility Due September 2029 [Member] Unsecured revolving credit facility maturing September 10, 2029 A contractual agreement to borrow and repay an amount under an unsecured term loan, due August 14, 2028. Unsecured Term Loan Due August 2028 [Member] Unsecured term loan maturing August 14, 2028 Represents the contractual arrangement to borrow and repay an amount under publicly traded senior unsecured notes due in 2030. Senior unsecured notes, interest payable semi-annually at 2.15%, effective rate of 2.27%, maturing August 15, 2030 Senior unsecured notes, interest payable semi-annually at 2.15%, effective rate of 2.27%, maturing August 15, 2030 A contractual arrangement to borrow and repay an amount under publicly traded senior unsecured notes due in November 15, 2036. Senior unsecured notes, interest payable semi-annually at 6.85%, effective rate of 6.91%, maturing November 15, 2036 Senior unsecured notes, interest payable semi-annually at 6.85%, effective rate of 6.91%, maturing November 15, 2036 Information relating to other notes and revolving credit facilities. Other notes Other notes Debt Instrument [Line Items] Debt Long-Term Debt, Gross Total Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Less: unamortized discount and debt issuance costs Semi-annual interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium. Debt Instrument Interest Rate Semi Annual Percentage Semi-annual rate (as a percent) Debt Instrument, Interest Rate, Effective Percentage Effective rate (as a percent) A contractual arrangement to borrow and repay an amount under publicly traded senior unsecured notes. Senior Unsecured Notes - Publicly Traded Senior Unsecured Notes - Publicly Traded Letter of Credit [Member] Letters of Credit Long-Term Debt, Type [Axis] Long-Term Debt, Type [Domain] Represents the overall credit agreement which consists of an unsecured revolving credit facility and a term loan. Standby Facility Standby Facility Variable Rate [Axis] Variable Rate [Domain] Secured Overnight Financing Rate (SOFR) [Member] SOFR Prime Rate [Member] Bank prime rate Line of Credit Facility, Maximum Borrowing Capacity Maximum borrowing capacity Debt Instrument, Term Debt term Debt Instrument, Description of Variable Rate Basis Variable interest rate Debt Instrument, Basis Spread on Variable Rate Interest rate added to base (as a percent) Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Commitment fee on unused portion of revolving credit facility (as a percent) Debt, Weighted Average Interest Rate Weighted average interest rate (as a percent) Letters of Credit Outstanding, Amount Letters of credit outstanding Debt Instrument, Redemption Price, Percentage Percentage of principal amount at which the notes may be required to be repurchased in event of a change of control and a downgrade of the entity's credit rating Lessee, Lease, Description [Table] Lessee, Lease, Description [Line Items] Leases Operating Lease, Payments Cash payments for operating leases Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Right-of-use assets obtained in exchange for operating lease obligations Effective Income Tax Rate Reconciliation, Percent Effective tax rate (as a percent) Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Income tax at U.S. federal statutory tax rate (as a percent) Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Restricted Stock Units (RSUs) [Member] Restricted stock units (RSUs) Details of restricted stock units (RSU) and performance stock units (PSU). Restricted stock units (RSUs) and performance stock units (PSUs) Restricted stock units (RSUs) and performance stock units (PSUs) Performance Shares [Member] Performance stock units (PSUs) Statistical Measurement [Axis] Statistical Measurement [Domain] Maximum [Member] Maximum Dividends [Axis] Dividends [Domain] Represents the regular quarterly dividend for Q3 in 2026. O 2026 Q3 Dividends [Member] Q3 2026 Dividends Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent event Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Stock Based Compensation Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage Disclosure of Repurchase Agreements [Abstract] Share Repurchase Plan Share Repurchase Program, Authorized, Amount Value of shares authorized by the Board of Directors to be repurchased under share repurchase plan Share Repurchase Program, Remaining Authorized, Amount Remaining value of shares authorized by the Board of Directors to be repurchased under share repurchase plan Stock Repurchased During Period, Shares Shares Shares Acquired, Average Cost Per Share Average Cost Per Share Treasury Stock, Value, Acquired, Cost Method Amount Shares Granted or Issued, Share-Based Payment Arrangement [Abstract] Common Stock and Additional Paid-In (in Shares) Dividends [Abstract] Dividends Represents the number of consecutive years of quarterly cash dividends paid. Number Of Consecutive Years Of Quarterly Cash Dividends Paid Number of consecutive years of quarterly cash dividends paid Common Stock, Dividends, Per Share, Cash Paid Common stock dividend quarterly declared and paid per share (in dollars per share) Dividends Payable, Date Declared Dividend date of declaration Dividends Payable, Date to be Paid Dividend date payable Dividends Payable, Date of Record Dividend date of record Share-Based Compensation Arrangement by Share-Based Payment Award, Additional General Disclosures [Abstract] Additional share-based compensation disclosures Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Vesting period (in years) Represents the period of return on assets results and including service criteria period. Share Based Compensation Arrangement By Share Based Payment Award Award Return On Assets Results And Including Service Criteria Period Return on assets result period Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Total unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Weighted average recognition period for unrecognized compensation cost (in years) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Changes Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Unvested as of the end of the period (in units) Unvested as of the beginning of the period (in units) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Granted (in units) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Vested (in units) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Cancelled or forfeited (in units) Common Stock, Capital Shares Reserved for Future Issuance Shares reserved for future issuance (all plans) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Weighted Average Grant Date Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Unvested as of the end of the period (in dollars per unit) Unvested as of the beginning of the period (in dollars per unit) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Granted (in dollars per unit) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Vested (in dollars per unit) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Cancelled or forfeited (in dollars per unit) Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member] Foreign Currency Translation Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member] Pension and Postretirement Benefit Plan Adjustments, Net of Tax Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Loss Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Change Earnings Per Share, Basic, by Common Class, Including Two-Class Method [Table] Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Earnings Per Share Net Income (Loss) Attributable to Parent [Abstract] Numerator: Net Income (Loss) Available to Common Stockholders, Basic Net income - Reliance Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Denominator: Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Dilutive effect of stock-based awards (in shares) Earnings Per Share, Diluted, Other Disclosure [Abstract] Diluted shares Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Weighted average shares, respectively, for RSUs and PSUs, not included in the diluted calculation due to their anti-dilutive effect Concentration Risk [Table] Concentration Risk [Line Items] Collective Bargaining Agreements Environmental Contingencies [Abstract] Environmental Contingencies Represents the parent entity's interest in net assets of the subsidiary, expressed as a percentage. Majority Interest Ownership Percentage by Parent Ownership interest in domestic subsidiaries (as a percent) Segment Reporting Information [Line Items] Segment Information Number of Reportable Segments Number of reportable segments Segments [Axis] Segments [Domain] Represents the Metals Service Centers segment. Metals Service Centers Segment {Member] Metals Service Centers Consolidation Items [Axis] Consolidation Items [Domain] Operating Segments [Member] Operating segments Compensation Expense, Excluding Cost of Good and Service Sold Compensation expense Segment Reporting, Other Segment Item, Amount Other segment items Segment Reporting Information, Additional Information [Abstract] Other Segment Disclosures Segment Reporting, Long-Lived Asset, Expenditure for Addition Purchases of property, plant and equipment