Document and Entity Information [Abstract] Document Information [Table] Legal Entity [Axis] Entity [Domain] Represents the entity's Employee Benefit Plan No. 003. E B P 003 [Member] Reliance, Inc. Master 401(k) Plan Document Information [Line Items] Document Entity Information Document Type Entity Registrant Name Entity Central Index Key Amendment Flag STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS EBP, Statement of Net Asset Available for Benefit [Table] EBP, Statement of Net Asset Available for Benefit [Line Items] STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS EBP, Asset [Abstract] Assets EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value Investments, at fair value EBP, Receivable [Abstract] Receivables: EBP, Note Receivable from Participant Notes receivable from participants EBP, Other Receivable Other receivables EBP, Receivable Total receivables EBP, Asset Total assets EBP, Liability [Abstract] Liabilities Amount of liability to trustee in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Liability to Trustee Due to trustee, net EBP, Other Liability Other payables Other payables EBP, Liability Total liabilities EBP, Net Asset Available for Benefit Net assets available for benefits, end of year Net assets available for benefits, beginning of year Net assets available for benefits STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Change in Net Asset Available for Benefit, Increase [Abstract] Additions EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Income: EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment Net appreciation in fair value of investments EBP, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment Interest and dividends EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Interest on notes receivable from participants EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment Total investment income EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] Contributions: EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover Participant EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash Employer, net of forfeitures EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Rollover EBP, Change in Net Asset Available for Benefit, Increase from Contribution Total contributions, net Amount of increase in net asset available for benefit from revenue sharing program credits to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Change in Net Asset Available For Benefit, Increase From Revenue Sharing Program Credits Revenue sharing program credits EBP, Change in Net Asset Available for Benefit, Increase Total additions EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Deductions EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Benefits paid EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Administrative expenses Recordkeeping and other Fidelity fees EBP, Change in Net Asset Available for Benefit, Decrease Total deductions Amount of increase (decrease) before transfers in net asset available for benefit to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Change in Net Asset Available for Benefit Before Transfers, Net Increase (Decrease) Net increase EBP, Change in Net Asset Available for Benefit, Transfer to (from) Plan Transfers from other plans EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Net increase in net assets available for benefits DESCRIPTION OF THE PLAN EBP, Description of Plan [Table] EBP, Description of Plan [Line Items] DESCRIPTION OF THE PLAN PLAN TERMINATION EBP, Description of Plan [Text Block] DESCRIPTION OF THE PLAN SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES EBP, Accounting Policy [Table] EBP, Accounting Policy [Line Items] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES EBP, Summary of Accounting Policy [Text Block] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES No definition available. RELIANCE, INC. STOCK FUND. Represents a table presenting information about investments held by the employee benefit plan, including investment types, fair values, units or shares held, and other related investment details as of the reporting date. Employee Benefit Plan, Investments [Table] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. RELIANCE, INC. STOCK FUND The entire disclosure of investments held by the employee benefit plan, including descriptions of investment types, investment strategies, fair value information, concentrations, risks and uncertainties, and other related investment information. Employee Benefit Plan, Investments [Text Block] RELIANCE, INC. STOCK FUND FAIR VALUE MEASUREMENTS EBP, Investment, Fair Value and NAV [Table] EBP, Investment, Fair Value and NAV [Line Items] FAIR VALUE MEASUREMENTS EBP, Investment, Fair Value and NAV [Text Block] FAIR VALUE MEASUREMENTS RELATED PARTY AND PARTY-IN-INTEREST TRANSACTIONS EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Related Party and Party-in-Interest Transactions [Line Items] RELATED PARTY AND PARTY-IN-INTEREST TRANSACTIONS EBP, Related Party and Party-in-Interest Transactions [Text Block] RELATED PARTY AND PARTY-IN-INTEREST TRANSACTIONS INCOME TAX STATUS EBP, Tax Status [Table] EBP, Tax Status [Line Items] INCOME TAX STATUS EBP, Tax Status [Text Block] INCOME TAX STATUS No definition available. PLAN TERMINATION EBP, Plan Termination [Text Block] PLAN TERMINATION No definition available. NONEXEMPT TRANSACTIONS Table presenting information about transactions involving the employee benefit plan that do not qualify for an exemption under ERISA or Internal Revenue Code prohibited transaction rules, including delinquent participant contributions, late loan repayments, related corrections, and associated lost earnings restoration amounts. Employee Benefit Plan, Non-exempt Transactions [Table] Employee Benefit Plan, Non-exempt Transactions [Table] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Employee Benefit Plan, Non-exempt Transactions [Line Items] NONEXEMPT TRANSACTIONS Textual disclosure of matters relating to non-exempt or prohibited transactions involving the employee benefit plan, including descriptions of delinquent participant contributions or loan repayments, timing of remittances, corrective actions taken, restoration of lost earnings, and related regulatory reporting requirements under ERISA and the Internal Revenue Code. Employee Benefit Plan, Non-exempt Transactions [Text Block] NONEXEMPT TRANSACTIONS RECONCILIATION OF FINANCIAL STATEMENTS TO FORM 5500 EBP, Reconciliation of Financial Statement to Form 5500 [Table] EBP, Reconciliation of Financial Statement to Form 5500 [Line Items] RECONCILIATION OF FINANCIAL STATEMENTS TO FORM 5500 EBP, Reconciliation of Financial Statement to Form 5500 [Text Block] RECONCILIATION OF FINANCIAL STATEMENTS TO FORM 5500 SUBSEQUENT EVENT EBP, Subsequent Event [Table] EBP, Subsequent Event [Line Items] SUBSEQUENT EVENT EBP, Subsequent Event [Text Block] SUBSEQUENT EVENT SCHEDULE H, LINE 4a - SCHEDULE OF DELINQUENT PARTICIPANT CONTRIBUTIONS EBP, Schedule of Delinquent Participant Contribution [Table] EBP, Schedule of Delinquent Participant Contribution [Line Items] SCHEDULE H, LINE 4a - SCHEDULE OF DELINQUENT PARTICIPANT CONTRIBUTIONS EBP, Schedule of Delinquent Participant Contribution [Text Block] SCHEDULE H, LINE 4a - SCHEDULE OF DELINQUENT PARTICIPANT CONTRIBUTIONS SCHEDULE H, LINE 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR) EBP, Schedule of Asset Held for Investment [Table] EBP, Schedule of Asset Held for Investment [Line Items] SCHEDULE H, LINE 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR) EBP, Schedule of Asset Held for Investment [Text Block] SCHEDULE H, LINE 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR) EBP, Basis of Accounting [Policy Text Block] Basis of Presentation EBP, Investment [Policy Text Block] Investment Valuation and Income Recognition Represents the accounting policy disclosure describing how the employee benefit plan recognizes and measures net appreciation or depreciation in the fair value of investments, including realized gains and losses from investment sales and unrealized changes in the fair value of investments held during the reporting period. Employee Benefit Plan, Net Appreciation (Depreciation) in Fair Value of Investments [Policy Text Block] Net Appreciation (Depreciation) in Fair Value of Investments EBP, Risk and Uncertainty [Policy Text Block] Risks and Uncertainties EBP, Use of Estimate [Policy Text Block] Use of Estimates EBP, Payment to Participant [Policy Text Block] Benefit Payments EBP, Subsequent Event [Policy Text Block] Subsequent Events Represents a table text block used to disclose detailed information about assets transferred into the employee benefit plan from other retirement plans, including plan mergers, acquisitions, and trustee-to-trustee transfers. This includes tabular breakdowns by source plan and corresponding amounts transferred during the reporting period. Employee Benefit Plan, Plan Transfers From Other Plans [Table Text Block] Schedule of transfers from other plans Represents a table text block used to disclose detailed information about vesting percentage into the employee benefit plan during the reporting period. Employee Benefit Plan, Vesting Percentage [Table Text Block] Schedule of vesting percentage of employee benefit plan Represents tabular disclosure of investments held by the employee benefit plan, including investment categories, units or shares held, fair values, and other related investment information presented in table format. Employee Benefit Plan, Investments [Table Text Block] Schedule of assets and liabilities of the Reliance, Inc. Stock Fund EBP, Investment, Fair Value and NAV [Table Text Block] Schedule of plan's investment assets at fair value EBP, Reconciliation of Financial Statement to Form 5500 [Table Text Block] Reconciliations of net assets and changes in net assets available for benefits as reported on Form 5500 with that reported in the accompanying financial statements Retirement Plan Name [Axis] Retirement Plan Name [Domain] Represents the American Alloy Steel 401(k) Plan, a qualified defined contribution retirement plan whose net assets were merged and transferred into the reporting employee benefit plan. American Alloy Steel 401(k) Plan [Member] American Alloy Steel 401(k) Plan Represents the Cooksey Iron & Metal Co., Inc. 401(k) Profit Sharing Plan, a qualified retirement plan whose participant balances and net assets were transferred into the reporting employee benefit plan. Cooksey Iron & Metal Co., Inc. 401(k) Profit Sharing Plan [Member] Cooksey Iron & Metal Co., Inc. 401(k) Profit Sharing Plan Represents the Southern Steel Supply 401(k) Plan, a qualified defined contribution retirement plan. Southern Steel Supply 401(k) Plan [Member] Southern Steel Supply 401(k) Plan Information by years of vesting service in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Years of Vesting Service [Axis] Employee Benefit Plan, Years of Vesting Service [Axis] Years of vesting service in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Years of Vesting Service [Domain] Employee Benefit Plan, Years of Vesting Service [Domain] Tranche one of years of vesting service in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Years of Vesting Service, Tranche One [Member] Less than 1 Tranche two of years of vesting service in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Years of Vesting Service, Tranche Two [Member] 1 Tranche three of years of vesting service in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Years of Vesting Service, Tranche Three [Member] 2 Tranche four of years of vesting service in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Years of Vesting Service, Tranche Four [Member] 3 Tranche five of years of vesting service in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Years of Vesting Service, Tranche Five [Member] 4 or more EBP, Description, Available [true false] Description of plan available Represents the number of days of employment required before an eligible employee may participate in the employee benefit plan. Employee Benefit Plan, Eligibility Waiting Period Participation eligibility waiting time period Represents the number of days following an employee's hire date before automatic enrollment in the employee benefit plan becomes effective. Employee Benefit Plan, Automatic Enrollment Waiting Period Participation automatic enrollment waiting time period EBP, Participant Contribution, Automatic, Deferral Rate Initial Contribution rate (as a percent) Percentage of automatic increase per year in pretax annual compensation that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), contributes to total pretax annual compensation. Employee Benefit Plan, Participant Contribution, Automatic Increase Per Year, Percent Increase in automatic deferral contributions, percent (as a percent) Percentage of maximum automatic salary deferral contribution rate under automatic enrollment. Employee Benefit Plan, Participant Contribution, Maximum Automatic Enrollment Contribution, Percent Maximum automatic deferral contributions, percent (as a percent) EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage Employee contribution, percentage (as a percent) Represents the minimum participant age required to qualify for enhanced or super catch-up contribution provisions under the employee benefit plan. Employee Benefit Plan, Super Catch Up Contribution, Minimum Eligible Age Minimum eligible age for super catch-up contributions Represents the maximum participant age eligible to qualify for enhanced or super catch-up contribution provisions under the employee benefit plan. Employee Benefit Plan, Super Catch Up Contribution, Maximum Eligible Age Maximum eligible age for super catch-up contribution Represents the percentage of vesting. Employee Benefit Plan, Vesting Percentage Vesting percentage (as a percent) Statistical Measurement [Axis] Statistical Measurement [Domain] Minimum [Member] Minimum Maximum [Member] Maximum Amount during the reporting period in forfeited nonvested participant account balances available for future allocation, restoration, or reduction of employer contributions and administrative expenses. Employee Benefit Plan Forfeited Nonvested Account During The Period Amount of forfeited nonvested contributions during the period EBP, Forfeited Nonvested Account, Decrease from Employer Contribution Amount of forfeited nonvested contributions used to offset employer contributions EBP, Forfeited Nonvested Account Forfeited non-vested contributions EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount Note receivable, maximum borrowing amount EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage Note receivable, maximum borrowing percentage of account balance (as a percent) Maximum repayment period permitted for participant general purpose loans under the employee benefit plan. Employee Benefit Plan, Participant Loan, General Purpose, Maximum Repayment Term General purpose loan, maximum repayment term Maximum repayment period permitted for participant loans used for the purchase of a primary residence under the employee benefit plan. Employee Benefit Plan, Participant Loan, Primary Residence, Maximum Repayment Term Primary residence loan, maximum repayment term EBP, Asset Held for Investment, Participant Loan, Interest Rate Loan interest rate (as a percent) EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Investment Interest income from Fidelity Amount of administrative expenses of the employee benefit plan offset through the application of suspense account balances and related interest earnings during the reporting period. Employe Benefit Plan, Administrative Expenses Offset by Suspense Account Administrative expenses offset by suspense account Investment Type [Axis] Investments [Domain] EBP, Employer, Common Stock Fund [Member] Reliance, Inc. stock fund Represents the number of units held in a unitized employer stock fund within an employee benefit plan at the reporting date. Employee Benefit Plan, Employer Stock Fund Units Held Number of shares in investment EBP, Investment, Excluding Plan Interest in Master Trust, Fair and Contract Value Interest-bearing cash Represents the total fair value of a unitized employer stock fund held by the employee benefit plan, including underlying employer common stock and related cash or liquidity components. Employee Benefit Plan, Employer Stock Fund Fair Value Fair value of the investment EBP, Investment, Number of Shares Number of shares Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member] Fair Value, Inputs, Level 1, Level 2, and Level 3 Fair Value, Inputs, Level 1 [Member] Level 1 Fair Value Measured at Net Asset Value Per Share [Member] Fair value at NAV Cash and Cash Equivalents [Member] Cash and cash equivalents Mutual Fund [Member] Mutual funds EBP, Employer, Common Stock [Member] Reliance, Inc. common stock EBP, Self-Directed Brokerage Account [Member] Self-directed brokerage accounts EBP, Pooled Separate Account [Member] Commingled funds Common Collective Trust [Member] Common collective trust EBP, Change in Net Asset Available for Benefit, Increase from Dividend Income on Investment Dividend on investment from Reliance, Inc. EBP, Tax Determination Letter, Obtained [true false] Determination letter obtained EBP, Tax Determination Letter, Date Determination letter date EBP, Tax Qualification Status [Extensible Enumeration] Tax qualification status Represents the percentage of vesting of participant accounts in the event of termination. Employee Benefit Plan, Vesting Percentage in Event of Termination Participant vesting percentage upon Plan termination Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event [Member] SUBSEQUENT EVENT EBP, Schedule of Delinquent Participant Contribution, Transferred Late to Plan Participant Contributions Transferred Late to the Plan Participant contributions transferred late to the Plan EBP, Schedule of Delinquent Participant Contribution, Corrected Participant contributions transferred late to the Plan that were corrected Total Fully Corrected Under VFCP and PTE 2002-51 EBP, Schedule of Delinquent Participant Contribution, Corrected Outside VFCP Contributions Corrected Outside VFCP Participant contributions transferred late to the Plan that were corrected EBP, Form 5500 Caption, Net Assets Net assets available for benefits as reported on the Form 5500 EBP, Reconciliation to Form 5500, Net Asset Available for Benefit, Contract Value to Current Value Adjustment Adjustment from fair market value per Trustee to NAV for the MIP EBP, Form 5500 Caption, Net Income (Loss) Net income as reported on the Form 5500 Amount of beginning period increase (decrease) in net asset available for benefit from current value in excess of (less than) contract value of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) to reconcile change in net asset available for benefit per financial statement to Form 5500 caption. Form 5500 is form provided by Department of the Treasury, Internal Revenue Service (IRS); Department of Labor (DOL), Employee Benefit Security Administration (EBSA); and Pension Benefit Guaranty Corporation (PBGC). Employee Benefit Plan Reconciliation To Form 5500 Change In Net Asset Available For Benefit Increase Decrease For Contract Value To Current Value Beginning Of Period Investment, Adjustment from fair market value per Trustee to NAV for the MIP - Beginning of year Amount of ending period increase (decrease) in net asset available for benefit from current value in excess of (less than) contract value of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) to reconcile change in net asset available for benefit per financial statement to Form 5500 caption. Form 5500 is form provided by Department of the Treasury, Internal Revenue Service (IRS); Department of Labor (DOL), Employee Benefit Security Administration (EBSA); and Pension Benefit Guaranty Corporation (PBGC). Employee Benefit Plan Reconciliation To Form 5500 Change In Net Asset Available For Benefit Increase Decrease For Contract Value To Current Value End Of Period Investment, Adjustment from fair market value per Trustee to NAV for the MIP - End of year Represents the information pertaining to Mid-West Materials, Inc. Employees 401(k) Profit Sharing Plan and Trust. Mid-West Materials, Inc. Employees 401(k) Profit Sharing Plan and Trust [Member] Mid-West Materials, Inc. Employees 401(k) Profit Sharing Plan and Trust Entity Tax Identification Number Entity tax identification number EBP, Plan Number Plan number EBP, Schedule of Delinquent Participant Contribution, Late Repayment Included [true false] EBP, Schedule of Delinquent Participant Contribution, Late Repayment Included [true false] EBP, Schedule of Delinquent Participant Contribution, Not Corrected Contributions Not Corrected Investment, Identifier [Axis] EBP, Investment, Issuer Name [Extensible Enumeration] Investment issuer name EBP, Investment, Current Value, Type [Extensible Enumeration] Investment type EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value Current Value EBP, Asset Held for Investment, Participant Loan, Maturity Date Participants loans latest maturity date EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution Participant loans EBP, Asset Held for Investment Total EBP, Asset Held for Investment, Party-in-Interest [true false] Investment party in interest EBP, Asset Held for Investment, Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Asset Held for Investment, Plan Interest in Master Trust, Participation Status [Extensible Enumeration]