Summary of Significant Accounting Policies (Details 2) (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
Numerator:
Net income available to common stockholders	$ 5,760	$ 4,328	$ 5,132	$ 2,705	$ 4,105	$ 3,694	$ 3,170	$ 1,662	$ 17,925	$ 12,631	$ 15,136
Denominator:
Denominator for basic earnings per share-weighted average shares (in shares)	5,663	5,661	5,661	5,658	5,656	5,656	5,656	5,649	5,659	5,651	5,640
Effect of Dilutive Securities:
Stock options (in shares)									13	5	1
Denominator for diluted earnings per share - adjusted weighted-average shares and assumed conversions (in shares)	5,692	5,670	5,663	5,678	5,663	5,661	5,660	5,657	5,672	5,656	5,641
Basic earnings per share (in dollar per share)	$ 1.02	$ 0.76	$ 0.91	$ 0.48	$ 0.73	$ 0.65	$ 0.56	$ 0.29	$ 3.17	$ 2.24	$ 2.68
Diluted earnings per share (in dollar per share)	$ 1.01	$ 0.76	$ 0.91	$ 0.48	$ 0.72	$ 0.65	$ 0.56	$ 0.29	$ 3.16	$ 2.23	$ 2.68