Exempt Party-in-Interest Transactions (Details) - Fastenal Company & Subsidiaries 401(k) and Employee Stock Ownership Plan	12 Months Ended
Dec. 31, 2025 USD ($) shares	Dec. 31, 2024 shares
Exempt Party-in-Interest Transactions [Line Items]
Dividends	$ 31,911,370
Fastenal Company common stock
Exempt Party-in-Interest Transactions [Line Items]
Number of Units (in shares) \| shares	7,888,493	7,930,834
Stock split conversion ratio		2
Purchases	$ 51,353,932
Selling price	53,356,148
Dividends	$ 6,869,846

EBP, Stock Split, Conversion Ratio

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- Definition

Amount of increase in net asset available for benefit from dividend income on investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

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-Topic 962
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- Definition

Cost of investment, excluding plan interest in master trust, acquired by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

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- Definition

Number of shares or units of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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- Definition

Amount of selling price for investment, excluding plan interest in master trust, sold by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

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- 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.

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