Reconciliation of Financial Statements to Form 5500 (Details) - Fastenal Company & Subsidiaries 401(k) and Employee Stock Ownership Plan - USD ($) |
12 Months Ended | |
|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
|
| Reconciliation of Financial Statements to Form 5500 [Line Items] | ||
| Net assets available for benefits per the financial statements | $ 1,228,841,014 | $ 1,058,809,107 |
| Excess contributions payable | 4,870 | 1,987 |
| Net assets available for benefits per the Form 5500 | 1,228,845,884 | 1,058,811,094 |
| Changes in net assets available for benefits per the Plan’s financial statements | ||
| Total additions per the financial statements | 260,577,779 | |
| 2025 excess contributions payable | 4,870 | |
| Total income per the Form 5500 | 260,582,649 | |
| Total deductions per the financial statements | (90,545,872) | |
| 2024 excess contributions payable | $ (1,987) | |
| Total expenses per the Form 5500 | $ (90,547,859) | |
| X | ||||||||||
- Definition EBP, Excess Contributions Payable No definition available.
|
| X | ||||||||||
- Definition EBP, Reconciliation to Form 5500, Excess Contributions Payable, Current Period No definition available.
|
| X | ||||||||||
- Definition EBP, Reconciliation to Form 5500, Excess Contributions Payable, Prior Period No definition available.
|
| X | ||||||||||
- Definition Amount of decrease in net asset available for benefit to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
|
| X | ||||||||||
- Definition Amount of increase in net asset available for benefit to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
|
| X | ||||||||||
- Definition Amount of net asset available for benefit as reported in Form 5500 caption for employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). 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). Reference 1: http://www.xbrl.org/2003/role/exampleRef
|
| X | ||||||||||
- Definition Amount of decrease in net asset available for benefit from total expenses as reported in Form 5500 caption for employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). 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). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Amount of increase in net asset available for benefit from total income as reported in Form 5500 caption for employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). 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). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Amount of asset less liability available to pay benefit of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, aggregation of participants' individual account balances. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- Definition 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. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Details
|