Earnings Per Share (Details) (USD $)	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
Basic Net Income per Common Share Available to Common Stockholders [Abstract]
Net income	$ 3,509,000	$ 3,647,000	$ 3,479,000	$ 3,390,000	$ 3,270,000	$ 2,679,000	$ 2,578,000	$ 2,845,000	$ 14,025,000	$ 11,372,000	$ 8,761,000
Preferred stock dividends									(4,252,000)	(3,576,000)	(2,240,000)
Net income available to common stockholders	2,405,000	2,543,000	2,374,000	2,451,000	2,331,000	1,760,000	1,567,000	2,138,000	9,773,000	7,796,000	6,521,000
Weighted average common shares outstanding									6,023,289	6,042,015	6,092,670
Basic earnings per common share	$ 400	$ 420	$ 390	$ 410	$ 390	$ 290	$ 260	$ 350	$ 1.62	$ 1.29	$ 1.07
Diluted Net Income per Common Share Available to Common Stockholders [Abstract]
Net income available to common stockholders	2,405,000	2,543,000	2,374,000	2,451,000	2,331,000	1,760,000	1,567,000	2,138,000	9,773,000	7,796,000	6,521,000
Effect of assumed preferred stock conversion									0	0	0
Net income applicable to diluted earnings per share									$ 9,773,000	$ 7,796,000	$ 6,521,000
Weighted average common shares outstanding									6,023,289	6,042,015	6,092,670
Dilutive potential common shares [Abstract]
Assumed conversion of stock options									4,473	10,515	24,057
Restricted stock awarded									116	1,741	0
Assumed conversion of preferred stock									0	0	0
Dilutive potential common shares									4,589	12,256	24,057
Diluted weighted average common shares outstanding									6,027,878	6,054,271	6,116,727
Diluted earnings per common share	$ 400	$ 420	$ 390	$ 410	$ 390	$ 290	$ 260	$ 350	$ 1.62	$ 1.29	$ 1.07
Stock options to purchase shares of common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share (in shares)									108,125	202,970	202,970
Average dilutive potential common shares associated with convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share (in shares)									2,290,110	1,998,652	1,122,833