Stockholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	0 Months Ended
Mar. 31, 2013	Mar. 31, 2012	Apr. 09, 2013 Subsequent Event [Member]
Schedule of Shareholders' Equity [Line Items]
Dividend declared date			Apr. 09, 2013
Dividend declared per share			$ 0.20
Dividends payment date			May 30, 2013
Dividends payable record date			May 02, 2013
Options vesting and exercisable period, maximum (in years)	8 years
Options termination period after the end of the relevant vesting period (in months)	13 months
Total stock-based compensation expense for the Fastenal stock option plan	$ 1,350	$ 1,050
Total unrecognized compensation expense	$ 18,337
Weighted average period over which total unrecognized compensation expense will be recognized (in years)	4 years 6 months

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Share Based Compensation Arrangement By Share Based Payment Award Expiration

+ References

No definition available.

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

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- Definition

Date the declared dividend will be paid, in CCYY-MM-DD format.

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Date the dividend to be paid was declared, in CCYY-MM-DD format.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

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-Publisher FASB

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-Number 95

-Paragraph 32

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Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

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- Definition

As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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-Number 95

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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