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, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net income	$ 4,443	$ 3,245	$ 4,777	$ 2,439	$ 3,224	$ 4,296	$ 4,804	$ 2,949	$ 14,904	$ 15,273	$ 17,925
Less: Net income allocated to unvested participating securities									234	135	0
Net income available to common stockholders									$ 14,670	$ 15,138	$ 17,925
Denominator:
Denominator for basic earnings per share-weighted average shares	5,709	5,699	5,699	5,690	5,686	5,686	5,683	5,673	5,700	5,681	5,659
Effect of dilutive securities:
Stock options									53	64	13
Denominator for diluted earnings per share - adjusted weighted-average shares and assumed conversions	5,757	5,742	5,754	5,757	5,751	5,754	5,745	5,738	5,753	5,745	5,672
Basic earnings per share	$ 0.77	$ 0.56	$ 0.83	$ 0.43	$ 0.56	$ 0.76	$ 0.85	$ 0.52	$ 2.57	$ 2.66	$ 3.17
Diluted earnings per share	$ 0.76	$ 0.56	$ 0.82	$ 0.42	$ 0.56	$ 0.75	$ 0.84	$ 0.51	$ 2.55	$ 2.64	$ 3.16