Common Shareholders' Equity - Summary of common shareholders' equity (Details) (USD $)	Common stock	Capital in excess of par value	Retained earnings	ESOP	Treasury stock	Accumulated Other Comprehensive Loss	Total
Balance at Dec. 31, 2010	$ 523,000	$ 13,491,000	$ 11,467,000	$ (1,367,000)	$ (2,724,000)	$ (78,000)	$ 21,312,000
Balance (shares) at Dec. 31, 2010	2,614,506
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			2,626,000				2,626,000
Retirement benefits adjustment						11,000	11,000
Compensation expense				101,000			101,000
Cash dividend			(682,000)				(682,000)
Surrender of unexercised options, net of tax benefit		176,000	(517,000)				(341,000)
Exercise of stock options, net of income tax benefit		107,000	(404,000)		514,000		217,000
Balance at Dec. 31, 2011	523,000	13,774,000	12,490,000	(1,266,000)	(2,210,000)	(67,000)	23,244,000
Balance (shares) at Dec. 31, 2011	2,614,506						2,614,506
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			320,000				320,000
Retirement benefits adjustment						(18,000)	(18,000)
Compensation expense				101,000			101,000
Purchase of treasury shares					(110,000)		(110,000)
Cash dividend			(716,000)				(716,000)
Exercise of stock options, net of income tax benefit		213,000	(323,000)		555,000		445,000
Balance at Dec. 31, 2012	$ 523,000	$ 13,987,000	$ 11,771,000	$ (1,165,000)	$ (1,765,000)	$ (85,000)	$ 23,266,000
Balance (shares) at Dec. 31, 2012	2,614,506						2,614,506