Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011		Dec. 31, 2010
Earnings Per Share [Abstract]
Net Income	$ 22,179	$ 21,933		$ 21,892
Basic Shares, in Shares	12,007	11,970	[1]	11,836	[1]
Basic Earnings, in Earnings Per Share	$ 1.85	$ 1.83	[1]	$ 1.85	[1]
Dilutive Average Shares Attributable to Stock Options, in Shares	10	12		36
Weighted Average Shares - Diluted, in Shares	12,017	11,982	[1]	11,872	[1]
Diluted Earnings, In Earnings Per Share	$ 1.85	$ 1.83	[1]	$ 1.84	[1]
Antidilutive Shares Excluded from the Calculation of Earnings Per Share, in Shares	203	136		70

[1] Share and Per Share Amounts have been restated for the September 2012 2% stock dividend.