Earnings Per Share (Schedule of Earnings per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic Earnings Per Share
Net income													$ 12,315	$ 13,241	$ 12,262
Income available to common stockholders	$ 1,460	$ 3,751	$ 3,898	$ 3,206	$ 3,237	$ 3,482	$ 4,157	$ 2,365	$ 3,338	$ 3,225	$ 3,218	$ 2,481	$ 12,315	$ 13,241	$ 12,262
Weighted-Average Shares number of common shares, basic													7,360,066	7,391,681	7,374,589
Weighted-Average Shares, effect of dilutive securities stock option													141,993	147,157	173,296
Weighted-Average Shares income available to common stockholders and assumed conversions, diluted													7,502,059	7,538,838	7,547,885
Earnings per share, basic	$ 0.20	$ 0.51	$ 0.53	$ 0.44	$ 0.44	$ 0.48	$ 0.56	$ 0.32	$ 0.45	$ 0.44	$ 0.44	$ 0.34	$ 1.67	$ 1.79	$ 1.66
Earnings per share, diluted	$ 0.19	$ 0.50	$ 0.52	$ 0.43	$ 0.43	$ 0.47	$ 0.55	$ 0.31	$ 0.44	$ 0.43	$ 0.43	$ 0.33	$ 1.64	$ 1.76	$ 1.62