Stockholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended		0 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Oct. 08, 2013 Subsequent Event [Member]
Schedule of Shareholders' Equity [Line Items]
Dividend declared date			Oct. 08, 2013
Dividend declared per share			$ 0.25
Dividends payment date			Nov. 22, 2013
Dividends payable record date			Oct. 25, 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	$ 4,050	$ 3,450
Total unrecognized compensation expense	$ 17,273
Weighted average period over which total unrecognized compensation expense will be recognized (in years)	4 years 11 months 1 day