Income Per Share of Common Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Per Share of Common Stock
Net income for basic and diluted income per common share	$ 5,426	$ 4,789	$ 15,636	$ 12,171
Weighted-average shares for basic income per share	5,578,000	5,563,000	5,578,000	5,560,000
Effect of dilutive securities:
Employee and director stock options (in shares)	11,000	11,000	10,000	10,000
Adjusted weighted-average shares and assumed exercises for diluted income per share	5,589,000	5,574,000	5,588,000	5,570,000
Basic net income per common share (in dollars per share)	$ 0.97	$ 0.86	$ 2.80	$ 2.19
Diluted net income per common share (in dollars per share)	$ 0.97	$ 0.86	$ 2.80	$ 2.19
Options
Anti-dilutive securities
Anti-dilutive shares of common stock excluded from the calculation of dilutive securities	15,000	9,900	15,000	9,900