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
Quarterly Financial Data [Abstract]
Interest income	$ 13,903	$ 13,958	$ 13,958	$ 13,948	$ 14,453	$ 14,168	$ 14,122	$ 14,029
Interest expense	1,214	1,348	1,700	1,895	1,911	2,026	2,243	2,324	6,157	8,504	10,756
Net interest income	12,689	12,610	12,258	12,053	12,542	12,142	11,879	11,705	49,610	48,268	40,127
Provision for loan losses	896	720	416	615	517	728	916	940
Net interest income after provision for loan losses	11,793	11,890	11,842	11,438	12,025	11,414	10,963	10,765	46,963	45,167	36,390
Other income	4,710	4,523	4,497	4,580	4,023	3,700	4,059	4,005	18,310	15,787	13,820
Other expense	10,877	10,562	10,782	10,617	10,886	10,864	11,011	10,292	42,838	43,053	36,927
Income before income taxes	5,626	5,851	5,557	5,401	5,162	4,250	4,011	4,478	22,435	17,901	13,283
Income taxes	2,117	2,204	2,078	2,011	1,892	1,571	1,433	1,633	8,410	6,529	4,522
Net income	3,509	3,647	3,479	3,390	3,270	2,679	2,578	2,845	14,025	11,372	8,761
Dividends on preferred shares	1,104	1,104	1,105	939	939	919	1,011	707	4,252	3,576	2,240
Net income available to common stockholders	$ 2,405	$ 2,543	$ 2,374	$ 2,451	$ 2,331	$ 1,760	$ 1,567	$ 2,138	$ 9,773	$ 7,796	$ 6,521
Basic earnings per common share	$ 400.00	$ 420.00	$ 390.00	$ 410.00	$ 390.00	$ 290.00	$ 260.00	$ 350.00	$ 1.62	$ 1.29	$ 1.07
Diluted earnings per common share	$ 400.00	$ 420.00	$ 390.00	$ 410.00	$ 390.00	$ 290.00	$ 260.00	$ 350.00	$ 1.62	$ 1.29	$ 1.07