Summary of Significant Accounting Policies (Details 3) (USD $) In Thousands, except 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
Summary of Significant Accounting Policies
Net income for basic and diluted income per common share	$ 3,731	$ 5,426	$ 5,718	$ 4,492	$ 2,628	$ 4,789	$ 4,626	$ 2,757	$ 19,367	$ 14,800	$ 16,423
Weighted-average shares for basic income per share									5,578,784	5,561,429	5,705,475
Effect of dilutive securities:
Employee and director stock options (in shares)									10,459	9,850	10,286
Adjusted weighted-average shares and assumed exercises for diluted income per share									5,589,243	5,571,279	5,715,761
Basic net income per common share (in dollars per share)	$ 0.67	$ 0.97	$ 1.03	$ 0.81	$ 0.47	$ 0.86	$ 0.83	$ 0.50	$ 3.47	$ 2.66	$ 2.88
Diluted net income per common share (in dollars per share)	$ 0.67	$ 0.97	$ 1.03	$ 0.80	$ 0.47	$ 0.86	$ 0.83	$ 0.50	$ 3.47	$ 2.66	$ 2.87
Options
Anti-dilutive securities
Anti-dilutive shares of common stock excluded from the calculation of dilutive securities									7,500	15,000	17,400