Income Per Share of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Per Share of Common Stock
Net income for basic and diluted income per common share	$ 4,066	$ 2,365
Weighted-average shares for basic income per share	5,577,000	5,597,000
Effect of dilutive securities:
Employee and director stock options (in shares)	3,000	8,000
Adjusted weighted-average shares and assumed exercises for diluted income per share	5,580,000	5,605,000
Basic net income per common share (in dollars per share)	$ 0.73	$ 0.42
Diluted net income per common share (in dollars per share)	$ 0.73	$ 0.42
Options
Anti-dilutive securities
Anti-dilutive shares of common stock excluded from the calculation of dilutive securities	35,000	17,000