Entity tax identification number Entity Tax Identification Number Rollover EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Maximum Maximum [Member] Forfeited nonvested account, decrease from administrative expense EBP, Forfeited Nonvested Account, Decrease from Administrative Expense Legal Entity [Axis] Legal Entity [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Description of Plan [Table] EBP, Description of Plan [Table] Mutual funds Mutual Fund [Member] Higher catch-up contribution age EBP, Roth Tax Treatment, Catch-Up Contribution Age EBP, Roth Tax Treatment, Catch-Up Contribution Age Subsequent Events Subsequent Event [Member] Selling price EBP, Investment Sold, Excluding Plan Interest in Master Trust, Selling Price Exempt Party-in-Interest Transactions [Table] EBP, Related Party and Party-in-Interest Transactions [Table] Minimum requisite service period EBP, Requisite Service Period EBP, Requisite Service Period Total deductions Total deductions per the financial statements EBP, Change in Net Asset Available for Benefit, Decrease Employer Contribution, Type [Domain] EBP, Employer Contribution, Type [Domain] EBP, Employer Contribution, Type [Domain] Fair Value Measurements EBP, Investment, Fair Value and NAV [Text Block] Total investments at fair value EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value Subsequent Event Type [Domain] Subsequent Event Type [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Reconciliation of Financial Statements to Form 5500 EBP, Reconciliation of Financial Statement to Form 5500 [Table Text Block] Stable value fund Stable Value Fund [Member] Stable Value Fund EBP, Investment, Fair Value and NAV [Abstract] Excess Contribution Payable EBP, Excess Contribution Payable [Policy Text Block] Total assets EBP, Asset Assets EBP, Asset [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Additions: EBP, Change in Net Asset Available for Benefit, Increase [Abstract] Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Table] Total expenses per the Form 5500 EBP, Form 5500 Caption, Total Expenses Benefits EBP, Payment to Participant [Policy Text Block] Amendment Flag Amendment Flag Basis of Presentation EBP, Basis of Accounting [Policy Text Block] Schedule of Asset Held for Investment [Table] EBP, Schedule of Asset Held for Investment [Table] Number of Units (in shares) EBP, Investment, Number of Shares EBP, Description of Plan and Accounting Change [Abstract] Receivables: EBP, Receivable [Abstract] Investments at Fair Value EBP, Investment, Fair Value and NAV [Table Text Block] Employer contribution vesting percentage EBP, Employee Contribution Vesting Percentage EBP, Employee Contribution Vesting Percentage Excess contributions payable EBP, Excess Contributions Payable EBP, Excess Contributions Payable Discretionary Profit Sharing Contribution EBP, Discretionary Contribution [Member] EBP, Discretionary Contribution Investments [Domain] Investments [Domain] Maximum number of distributions per year EBP, Maximum Number Of Distributions Per Year EBP, Maximum Number Of Distributions Per Year Use of Estimates EBP, Use of Estimate [Policy Text Block] Form 5500, Schedule H, Part IV, Line 4i – Schedule of Assets (Held At End of Year) EBP, Schedule of Asset Held for Investment [Text Block] Cover [Abstract] Changes in net assets available for benefits per the Plan’s financial statements EBP, Reconciliation to Form 5500, Change in Net Asset Available for Benefit, Increase (Decrease) from Deemed Distribution [Abstract] Employer EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash Minimum Minimum [Member] Investment Type [Axis] Investment Type [Axis] Total contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution Participant EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover Net appreciation in fair value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment Minimum age to contribute EBP, Employer Contribution, Minimum Age EBP, Employer Contribution, Minimum Age Description of Plan [Line Items] EBP, Description of Plan [Line Items] Number of changes after period end EBP, Number Of Changes After Period End EBP, Number Of Changes After Period End Plan number EBP, Plan Number Investments at Fair Value [Line Items] EBP, Investment, Fair Value and NAV [Line Items] Plan Description EBP, Description of Plan [Text Block] Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] Statement of Net Asset Available for Benefit [Table] EBP, Statement of Net Asset Available for Benefit [Table] Minimum annual compensation to total compensation, percentage EBP, Participant Contribution, Minimum Annual Compensation to Total Compensation, Percentage EBP, Participant Contribution, Minimum Annual Compensation to Total Compensation, Percentage Schedule of Asset Held for Investment [Line Items] EBP, Schedule of Asset Held for Investment [Line Items] Fastenal Company common stock EBP, Employer, Common Stock [Member] EBP, Schedule of Asset Held for Investment [Abstract] Accounting Policy [Table] EBP, Accounting Policy [Table] Total additions Total additions per the financial statements EBP, Change in Net Asset Available for Benefit, Increase Investment income: EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Maximum number of partial distributions In plan year EBP, Payment Of Benefits, Maximum Number Of Partial Distributions In Plan Year EBP, Payment Of Benefits, Maximum Number Of Partial Distributions In Plan Year Investment, Identifier [Axis] Investment, Identifier [Axis] Administrative expenses EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Employer Contribution, Type [Axis] EBP, Employer Contribution, Type [Axis] EBP, Employer Contribution, Type Risk and Uncertainties EBP, Risk and Uncertainty [Policy Text Block] Document Information [Line Items] Document Information [Line Items] Stock split conversion ratio EBP, Stock Split, Conversion Ratio EBP, Stock Split, Conversion Ratio EBP, Statement of Change in Net Asset Available for Benefit [Abstract] Level 2 Fair Value, Inputs, Level 2 [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Tax Status [Table] EBP, Tax Status [Table] Net increase in net assets EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Exempt Party-in-Interest Transactions EBP, Related Party and Party-in-Interest Transactions [Text Block] EBP, Related Party and Party-in-Interest Transactions [Abstract] EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] Excess contributions payable EBP, Excess Contribution Payable Total receivables EBP, Receivable Employer contribution EBP, Employer Contribution, Receivable Automatic deferral rate EBP, Participant Contribution, Automatic, Deferral Rate Total investments at fair value EBP, Investment, Fair Value [Abstract] Benefits paid to participants EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Dividends EBP, Change in Net Asset Available for Benefit, Increase from Dividend Income on Investment Current Value EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] EBP, Statement of Net Asset Available for Benefit [Abstract] Accounting Policy [Line Items] EBP, Accounting Policy [Line Items] Total income per the Form 5500 EBP, Form 5500 Caption, Total Income EBP, Tax Status [Abstract] Reconciliation of Financial Statements to Form 5500 [Table] EBP, Reconciliation of Financial Statement to Form 5500 [Table] Reconciliation of Financial Statements to Form 5500 [Line Items] 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] Maximum percentage of contribution investment in company stock EBP, Investment Options, Maximum Contribution Investment In Company Stock, Percentage EBP, Investment Options, Maximum Contribution Investment In Company Stock, Percentage Investment Valuation and Income Recognition EBP, Investment [Policy Text Block] Participant contributions EBP, Participant Contribution, Receivable Total Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member] Document Type Document Type 2025 excess contributions payable EBP, Reconciliation to Form 5500, Excess Contributions Payable, Current Period EBP, Reconciliation to Form 5500, Excess Contributions Payable, Current Period Entity Central Index Key Entity Central Index Key EBP, Reconciliation of Financial Statement to Form 5500 [Abstract] Common/collective trust funds Common Collective Trust [Member] Tax Status [Line Items] EBP, Tax Status [Line Items] Subsequent Events [Table] EBP, Subsequent Event [Table] Deductions: EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Summary of Significant Accounting Policies EBP, Summary of Accounting Policy [Text Block] Entity Registrant Name Entity Registrant Name Purchases EBP, Investment Acquired, Excluding Plan Interest in Master Trust, Cost EBP, Subsequent Event [Abstract] Liabilities EBP, Liability [Abstract] Fastenal Company & Subsidiaries 401(k) and Employee Stock Ownership Plan EBP 001 [Member] EBP 001 Maximum annual compensation deferral percentage EBP, Participant Contribution, Maximum Annual Compensation to Total Compensation, Percentage EBP, Participant Contribution, Maximum Annual Compensation to Total Compensation, Percentage Subsequent Events EBP, Subsequent Event [Text Block] Tax Status EBP, Tax Status [Text Block] Risk and Uncertainty, Concentration of Investment at Fair Value to Total Investments, Percentage EBP, Risk and Uncertainty, Concentration of Investment at Fair Value to Total Investments, Percentage Subsequent Events [Line Items] EBP, Subsequent Event [Line Items] Document Information [Table] Document Information [Table] Net investment income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment 2024 excess contributions payable EBP, Reconciliation to Form 5500, Excess Contributions Payable, Prior Period EBP, Reconciliation to Form 5500, Excess Contributions Payable, Prior Period Exempt Party-in-Interest Transactions [Line Items] EBP, Related Party and Party-in-Interest Transactions [Line Items] Level 3 Fair Value, Inputs, Level 3 [Member] Minimum number of partial distributions EBP, Payment Of Benefits, Minimum Number Of Partial Distributions EBP, Payment Of Benefits, Minimum Number Of Partial Distributions Net assets available for benefits Beginning of year End of year Net assets available for benefits per the financial statements EBP, Net Asset Available for Benefit Entity [Domain] Entity [Domain] Contributions: EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] Forfeited nonvested account EBP, Forfeited Nonvested Account Net assets available for benefits per the Form 5500 EBP, Form 5500 Caption, Net Assets Investments at Fair Value [Table] EBP, Investment, Fair Value and NAV [Table] Statement of Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Line Items]