Stockholders' Equity (Details 4) (2002 Directors Stock Plan [Member], USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
2002 Directors Stock Plan [Member]
Summary of Changes in Shares Available for Directors Stock Plan [Abstract]
Number of shares available, beginning of year	49,548	74,120	97,390
Additional shares available due to 2011 amendment to the Directors stock plan	200,000
Shares granted and issued	(18,630)	(12,500)	(16,289)
Shares granted and deferred	(7,762)	(12,072)	(6,981)
Number of shares available, end of year	223,156	49,548	74,120
Weighted average per share market value of awards on grant date	$ 25.77	$ 21.72	$ 19.34