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					9,245,262		9,245,262
Other comprehensive loss				(161,557)			(161,557)
Grant of stock options			187,510				187,510
Sale of treasury stock			(97,983)			344,961	246,978
Conversion Class C to Class A	646	(645)	(1)
Balance at Sep. 30, 2012	19,278,242	2,026,550	19,577,091	492,886	31,791,885	(2,417,874)	70,748,780
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					6,099,002		6,099,002
Other comprehensive loss				(621,887)			(621,887)
Grant of stock options			66,711				66,711
Exercise of stock options	714,572	422,422	(344,545)			(543,334)	249,115
Sale of treasury stock			321,824			195,120	516,944
Stock Dividends	(200)		(526)		726
Conversion Class C to Class A	83,246	(83,245)	(1)
Balance at Sep. 30, 2013	$ 22,484,770	$ 2,533,997	$ 21,305,603	$ 1,312,472	$ 41,213,800	$ (2,728,648)	$ 86,121,994