Common Stock and Earnings per Share (Schedule of Calculations of Basic and Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Basic
Net Income	$ 5,786	$ 6,401	$ 6,035	$ 5,811	$ 5,254	$ 6,138	$ 6,073	$ 6,032	$ 24,033	$ 23,497	$ 23,303
Weighted-average common shares outstanding (in shares)									11,479,025	11,441,158	11,378,216
Basic earnings per share (in dollars per share)	$ 0.50	$ 0.56	$ 0.52	$ 0.51	$ 0.45	$ 0.54	$ 0.53	$ 0.53	$ 2.09	$ 2.05	$ 2.05
Diluted
Net Income	$ 5,786	$ 6,401	$ 6,035	$ 5,811	$ 5,254	$ 6,138	$ 6,073	$ 6,032	$ 24,033	$ 23,497	$ 23,303
Weighted-average common shares outstanding (in shares)									11,479,025	11,441,158	11,378,216
Effect of dilutive restricted stock, stock options and SARs (in shares)									164,954	199,581	178,998
Weighted-average common shares outstanding assuming dilution (in shares)									11,643,979	11,640,739	11,557,214
Diluted earnings per share (in dollars per share)	$ 0.49	$ 0.55	$ 0.52	$ 0.50	$ 0.45	$ 0.53	$ 0.52	$ 0.52	$ 2.06	$ 2.02	$ 2.02