Summary of Significant Accounting Policies (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Numerator:
Net income	$ 3,224	$ 4,296	$ 4,804	$ 2,949	$ 5,760	$ 4,328	$ 5,132	$ 2,705	$ 15,273	$ 17,925	$ 12,631
Less: Net income allocated to unvested participating securities									135	0	0
Net income available to common stockholders									$ 15,138	$ 17,925	$ 12,631
Denominator:
Denominator for basic earnings per share-weighted average shares	5,686	5,686	5,683	5,673	5,663	5,661	5,661	5,658	5,681	5,659	5,651
Effect of dilutive securities:
Stock options									64	13	5
Denominator for diluted earnings per share - adjusted weighted-average shares and assumed conversions	5,751	5,754	5,745	5,738	5,692	5,670	5,663	5,678	5,745	5,672	5,656
Basic earnings per share	$ 0.56	$ 0.76	$ 0.85	$ 0.52	$ 1.02	$ 0.76	$ 0.91	$ 0.48	$ 2.66	$ 3.17	$ 2.24
Diluted earnings per share	$ 0.56	$ 0.75	$ 0.84	$ 0.51	$ 1.01	$ 0.76	$ 0.91	$ 0.48	$ 2.64	$ 3.16	$ 2.23