Stock Options (Schedule of Non-Qualified Stock Options Activity) (Details) (Non Qualified Options, USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Non Qualified Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding at beginning of year	112,800		102,400		186,000
Granted	0		30,000		0
Exercised	(23,100)		(14,600)		(78,600)
Canceled	0		(5,000)		(5,000)
Options outstanding at end of year	89,700		112,800		102,400
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding at beginning of year, Exercise Price, in dollars per share	$ 18.62	[1]	$ 15.62	[1]	$ 14.57	[1]
Granted, Exercise Price, in dollars per share	$ 0.00	[1]	$ 26.45	[1]	$ 0.00	[1]
Exercised, Exercise Price, in dollars per share	$ 13.62	[1]	$ 11.45	[1]	$ 12.52	[1]
Cancelled, Exercise Price, in dollars per share	$ 0.00	[1]	$ 25.18	[1]	$ 25.18	[1]
Outstanding at end of year, Exercise Price, in dollars per share	$ 19.91	[1]	$ 18.62	[1]	$ 15.62	[1]
Options exercisable at end of year	38,100		37,400		30,300
Excercisable at end of year, Exercise Price, in dollars per share	$ 21.91	[1]	$ 19.57	[1]	$ 20.79	[1]
Options available for grant at end of year	322,750		320,500		364,000

[1] Weighted Averages