Stockholders' Equity - Additional Information (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended		0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Oct. 09, 2014 Subsequent Event [Member]
Schedule of Shareholders' Equity [Line Items]
Dividend declared date			Oct. 09, 2014
Dividend declared per share			$ 0.25
Dividends payment date			Nov. 21, 2014
Dividends payable record date			Oct. 24, 2014
Options vesting and exercisable period, maximum	8 years
Options termination period	9 years
Total stock-based compensation expense for the Fastenal stock option plan	$ 4,620	$ 4,050
Total unrecognized stock-based compensation expense	$ 18,725
Weighted average period over which total unrecognized stock-based compensation expense will be recognized	4 years 7 months 13 days