Statements of Stockholders' Equity (USD $)	Class A Common Stock	Class C Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock	Total
Balance at Dec. 31, 2011	$ 19,277,596	$ 2,027,195	$ 19,487,565	$ 654,443	$ 22,546,623	$ (2,762,835)	$ 61,230,587
Net earnings					1,662,183		1,662,183
Other comprehensive income				979,930			979,930
Grant of stock options			47,218				47,218
Sale of treasury stock			(41,121)			96,635	55,514
Balance at Mar. 31, 2012	19,277,596	2,027,195	19,493,662	1,634,373	24,208,806	(2,666,200)	63,975,432
Balance at Dec. 31, 2012	21,687,152	2,194,820	21,262,140	1,934,359	35,114,072	(2,380,434)	79,812,109
Net earnings					2,033,266		2,033,266
Other comprehensive income				(375,426)			(375,426)
Grant of stock options			52,969				52,969
Exercise of stock options	204,206	86,677	(74,155)				216,728
Sale of treasury stock			63,986			19,727	83,713
Conversion Class C to Class A	1,818	(1,819)	1
Balance at Mar. 31, 2013	$ 21,893,176	$ 2,279,678	$ 21,304,941	$ 1,558,933	$ 37,147,338	$ (2,360,707)	$ 81,823,359