Stockholders' Equity (Narrative) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009
Stockholders' Equity [Abstract]
Dividend declared date	Jan. 17, 2012
Dividend declared per share	$ 0.17
Dividends payment date	Feb. 29, 2012
Dividends payable record date	Feb. 01, 2012
Dividends paid per share	$ 0.65	$ 0.62	$ 0.36
Total intrinsic value of stock options exercised	$ 4,977	$ 0	$ 0
Options termination period after the end of the relevant vesting period (in months)	13
Total stock-based compensation expense for the Fastenal option plan	4,050	4,030	3,850
Total unrecognized compensation expense	15,145
Weighted average period over which total unrecognized compensation expense will be recognized (in years)	4.70
Total fair value of shares vested	$ 9,168	$ 1,125	$ 2,080
Options vesting and exercisable, maximum (in years)	eight

Share-Based Compensation Arrangement By Share Based Payment Award, Options Vested, Fair Value

No definition available.

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- Definition

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

+ References

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

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- Definition

The day, month, and year (YYYY-MM-DD) that the dividend declared as of or prior to the financial reporting date will be paid in the subsequent period.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

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- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 32

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- Definition

The day, month and year (YYYY-MM-DD) that the dividend to be paid was declared.

+ References

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- Definition

The date as of when a holder must own the stock to be entitled to the dividend. The ex-dividend date is generally 3 days before the record date.

+ References

No definition available.

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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.

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph h

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

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- Definition

The weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years.

+ References

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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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-Publisher FASB

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-Paragraph 28

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- Definition

The date when the equity-based award expires as specified in the award agreement, which may be presented in a variety of ways (for example, year, month and year, day, month and year, quarter of a year).

+ References

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-Number 123R

-Paragraph A240

-Subparagraph a

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- Definition

Description of the period of time over 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, which may be expressed in a variety of ways (for example, in years, month and year).

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph a

-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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- Definition

The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

+ References

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-Number 123R

-Paragraph A240

-Subparagraph c(2)

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