Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per 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
Quarterly Financial Information Disclosure [Abstract]
Interest Income	$ 20,532	$ 20,348	$ 19,825	$ 19,681	$ 20,032	$ 18,812	$ 18,458	$ 18,370	$ 80,386	$ 75,672	$ 77,160
Net Interest Income	19,031	18,791	18,321	18,196	18,388	17,192	16,712	16,225	74,339	68,517	66,248
Net Income	$ 7,644	$ 7,708	$ 6,687	$ 6,305	$ 6,589	$ 6,483	$ 6,532	$ 5,809	$ 28,344	$ 25,413	$ 24,055
Basic Earnings (in usd per share)	$ 0.58	$ 0.58	$ 0.51	$ 0.48	$ 0.50	$ 0.51	$ 0.52	$ 0.46	$ 2.15	$ 1.99	$ 1.91
Diluted Earnings (in usd per share)	$ 0.58	$ 0.58	$ 0.51	$ 0.48	$ 0.50	$ 0.51	$ 0.52	$ 0.46	$ 2.14	$ 1.98	$ 1.90