Stockholders' Equity (Narrative) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended			0 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jan. 16, 2013 Subsequent Event [Member]
Schedule of Shareholder's Equity [Line Items]
Dividend declared date				Jan. 16, 2013
Dividend declared per share				$ 0.10
Dividends payment date				Mar. 01, 2013
Dividends payable record date				Feb. 01, 2013
Dividends paid per share	$ 1.24	$ 0.65	$ 0.62
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 intrinsic value of stock options exercised	$ 34,424	$ 4,977	$ 0
Total unrecognized compensation expense	20,131
Weighted average period over which total unrecognized compensation expense will be recognized (in years)	4 years 8 months 9 days
Total fair value of shares vested	3,866	9,168	1,125
Total stock-based compensation expense for the Fastenal option plan	$ 4,800	$ 4,050	$ 4,030