Selected Quarterly Financial Data (Unaudited) (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, 2012	Dec. 31, 2011	Dec. 31, 2010
Selected Quarterly Financial Data (Unaudited) [Abstract]
Interest income	$ 21,439	$ 22,262	$ 22,726	$ 23,283	$ 23,040	$ 22,512	$ 22,157	$ 21,998	$ 89,710	$ 89,707	$ 75,949
Interest expense	1,585	1,710	1,837	1,981	2,171	2,430	2,669	2,711	7,113	9,981	11,830
Net interest income	19,854	20,552	20,889	21,302	20,869	20,082	19,488	19,287	82,597	79,726	64,119
Provision for loan losses	3,746	1,250	2,748	2,000	1,868	2,500	2,682	3,000	7,100	10,500	12,150
Net interest income after provision for loan losses	16,108	19,302	18,141	19,302	19,001	17,582	16,806	16,287	72,853	69,676	50,633
Noninterest income	4,603	1,358	988	1,297	1,427	1,431	2,622	3,732	8,246	9,212	33,531
Noninterest expense	13,972	13,663	15,109	13,655	14,291	13,807	13,671	14,056	56,399	55,825	46,797
Income before provision for income tax	6,739	6,997	4,020	6,944	6,137	5,206	5,757	5,963	24,700	23,063	37,367
Provision for income tax	2,153	2,359	1,173	2,171	1,898	1,581	1,745	1,887	7,856	7,111	11,797
Net income before preferred dividends					4,239	3,625	4,012	4,076	16,844	15,952	25,570
Preferred dividends					0	0	0	1,084	0	1,084	1,659
Net income available to common shareholders	$ 4,586	$ 4,638	$ 2,847	$ 4,773	$ 4,239	$ 3,625	$ 4,012	$ 2,992	$ 16,844	$ 14,868	$ 23,911
Basis earnings per share (in dollars per share)	$ 0.30	$ 0.30	$ 0.18	$ 0.31	$ 0.28	$ 0.24	$ 0.26	$ 0.20	$ 1.09	$ 0.97	$ 1.56
Diluted earnings per share (in dollars per share)	$ 0.30	$ 0.30	$ 0.18	$ 0.31	$ 0.28	$ 0.24	$ 0.26	$ 0.19	$ 1.09	$ 0.97	$ 1.55
Cash dividends declared per share (in dollars per share)	$ 0.15	$ 0.09	$ 0.14	$ 0.12	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.50	$ 0.20	$ 0.14