Summary of Quarterly Results (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary Of Quarterly Results Details
Total interest and dividend income	$ 6,937	$ 6,933	$ 6,679	$ 6,695	$ 7,063	$ 7,095	$ 7,113	$ 7,043	$ 7,366	$ 7,612	$ 7,473	$ 7,214	$ 27,244	$ 28,314	$ 29,665
Total interest expense	1,643	1,770	1,799	1,879	2,003	2,228	2,247	2,279	2,466	2,593	2,678	2,829	7,091	8,757	10,566
Net interest income	5,294	5,163	4,880	4,816	5,060	4,867	4,866	4,764	4,900	5,019	4,795	4,385	20,153	19,557	19,099
Provision for loan losses	460		165	160	240	360	430	360	240	510	585	460	785	1,390	1,795
Total noninterest income	1,559	1,444	2,323	1,242	1,376	1,367	1,197	1,397	1,512	1,463	1,297	1,091	6,568	5,337	5,363
Net income	$ 1,685	$ 1,226	$ 1,918	$ 1,180	$ 1,400	$ 1,394	$ 1,226	$ 1,285	$ 1,334	$ 1,331	$ 1,208	$ 881	$ 6,009	$ 5,305	$ 4,754
Basic earnings per share	$ 1.01	$ 0.74	$ 1.15	$ 0.70	$ 0.85	$ 0.85	$ 0.74	$ 0.78	$ 0.81	$ 0.81	$ 0.73	$ 0.53	$ 3.61	$ 3.21	$ 2.89
Diluted earnings per share	$ 1.01	$ 0.74	$ 1.15	$ 0.70	$ 0.85	$ 0.84	$ 0.74	$ 0.78	$ 0.81	$ 0.81	$ 0.73	$ 0.53	$ 3.61	$ 3.21	$ 2.89