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	$ 13,965	$ 13,807	$ 13,600	$ 13,362	$ 13,605	$ 13,446	$ 13,206	$ 13,202	$ 54,734	$ 53,459	$ 55,767
Interest expense	844	805	788	815	848	824	865	998	3,252	3,535	6,157
Net interest income	13,121	13,002	12,812	12,547	12,757	12,622	12,341	12,204	51,482	49,924	49,610
Provision charged to expense	134	44	128	323	486	975	252	480	629	2,193	2,647
Net interest income after provision for loan losses	12,987	12,958	12,684	12,224	12,271	11,647	12,089	11,724	50,853	47,731	46,963
Other income	4,496	4,402	4,990	4,481	4,380	5,697	4,714	4,550	18,369	19,341	18,310
Other expense	11,243	11,090	11,214	10,960	10,892	11,082	10,918	10,612	44,507	43,504	42,838
Income before income taxes	6,240	6,270	6,460	5,745	5,759	6,262	5,885	5,662	24,715	23,568	22,435
Income taxes	2,330	2,355	2,431	2,138	2,140	2,352	2,220	2,134	9,254	8,846	8,410
Net income	3,910	3,915	4,029	3,607	3,619	3,910	3,665	3,528	15,461	14,722	14,025
Dividends on preferred shares	839	1,105	1,104	1,104	1,104	1,104	1,105	1,104	4,152	4,417	4,252
Net income available to common stockholders	$ 3,071	$ 2,810	$ 2,925	$ 2,503	$ 2,515	$ 2,806	$ 2,560	$ 2,424	$ 11,309	$ 10,305	$ 9,773
Basic earnings per common share	$ 0.48	$ 0.48	$ 0.49	$ 0.43	$ 0.43	$ 0.47	$ 0.43	$ 0.41	$ 1.88	$ 1.74	$ 1.62
Diluted earnings per common share	$ 0.47	$ 0.47	$ 0.48	$ 0.43	$ 0.42	$ 0.47	$ 0.43	$ 0.41	$ 1.85	$ 1.73	$ 1.62