Consolidated Statements of Stockholders' Equity [Parenthetical] (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Dividends per share (in dollars per share)	$ 0.72	[1]	$ 0.69	[1]	$ 0.66	[1]
Exercise of stock options (in shares)	554		5,228		21,793
Excess tax benefit related to stock option plans (in dollars)	$ 1		$ 12		$ 40
stock dividend (in shares)	138,895		132,107		125,319
Stock Dividend Percentage	5.00%		5.00%		5.00%

[1] Dividends per share have been adjusted to give effect to the 5% stock dividends paid during December 2012, 2011 and 2010.