Quarterly Results of Operations (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	$ 22,317	$ 22,422	$ 22,289	$ 21,393	$ 21,419	$ 21,891	$ 22,481	$ 22,426	$ 88,421	$ 88,217	$ 90,947
Interest expense	3,056	3,048	3,041	2,983	3,069	3,184	3,231	3,258	12,128	12,742	17,202
Net interest income	19,261	19,374	19,248	18,410	18,350	18,707	19,250	19,168	76,293	75,475	73,745
Provision for credit losses	545	539	643	493	(6)	665	695	674	2,220	2,028	3,816
Non-interest income	6,196	5,949	6,504	5,685	8,614	6,475	6,376	6,336	24,334	27,801	23,412
Non-interest expense	16,301	15,179	15,792	15,125	18,986	15,199	15,648	16,500	62,397	66,333	59,031
Income before income tax	8,611	9,605	9,317	8,477	7,984	9,318	9,283	8,330	36,010	34,915	34,310
Income tax expense	2,523	3,154	3,001	2,762	3,560	2,952	2,952	2,668	11,440	12,132	10,882
Net income	$ 6,088	$ 6,451	$ 6,316	$ 5,715	$ 4,424	$ 6,366	$ 6,331	$ 5,662	$ 24,570	$ 22,783	$ 23,428
Per common share:
Basic earnings per share	$ 0.82	$ 0.87	$ 0.85	$ 0.76	$ 0.58	$ 0.83	$ 0.83	$ 0.74	$ 3.29	$ 2.98	$ 3.06
Diluted earnings per share	$ 0.82	$ 0.86	$ 0.85	$ 0.75	$ 0.58	$ 0.83	$ 0.82	$ 0.74	$ 3.28	$ 2.97	$ 3.05