Condensed Consolidated Statements of Stockholders’ Equity (Unaudited) - USD ($)	Class A Common Stock	Class C Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Retained Earnings	Treasury Stock	Total
Stockholders' Equity Attributable to Parent, Beginning Balance at Dec. 31, 2018	$ 30,609,596	$ 4,387,286	$ 41,821,778	$ (2,823)	$ 95,201,732	$ (206,396)	$ 171,811,173
Net earnings					1,930,318		1,930,318
Other comprehensive loss				820			820
Stock-based compensation expense			64,704				64,704
Exercise of stock options	8,936		8,444				17,380
Sale of treasury stock			295,153			42,343	337,496
Purchase of treasury stock						(112,404)	(112,404)
Stock dividends	282	(4)	489		(769)		(2)
Conversion Class C to Class A	6,560	(6,560)
Stockholders' Equity Attributable to Parent, Ending Balance at Mar. 31, 2019	30,625,374	4,380,722	42,190,568	(2,003)	97,131,281	(276,457)	174,049,485
Net earnings					3,480,054		3,480,054
Other comprehensive loss				716			716
Stock-based compensation expense			65,037				65,037
Exercise of stock options	20,274		9,519				29,793
Sale of treasury stock			92,605			25,190	117,795
Purchase of treasury stock						(174,704)	(174,704)
Conversion Class C to Class A	12	(14)	2
Stockholders' Equity Attributable to Parent, Ending Balance at Jun. 30, 2019	30,645,660	4,380,708	42,357,731	(1,287)	100,611,335	(425,971)	177,568,176
Stockholders' Equity Attributable to Parent, Beginning Balance at Dec. 31, 2019	32,215,558	5,001,774	46,091,112	13,726,514	101,256,229	(1,580,582)	196,710,605
Net earnings					1,424,449		1,424,449
Other comprehensive loss				(8,852,313)			(8,852,313)
Stock-based compensation expense			65,877				65,877
Exercise of stock options	44,822		(33,930)				10,892
Sale of treasury stock			218,280			264,081	482,361
Purchase of treasury stock						(129,608)	(129,608)
Stock dividends	2,322	(1,020)	2,292		(3,594)
Conversion Class C to Class A	22,324	(22,324)
Stockholders' Equity Attributable to Parent, Ending Balance at Mar. 31, 2020	32,285,026	4,978,430	46,343,631	4,874,201	102,677,084	(1,446,109)	189,712,263
Net earnings					20,557,047		20,557,047
Other comprehensive loss				12,019,888			12,019,888
Stock-based compensation expense			101,520				101,520
Exercise of stock options	22,726		(22,726)
Sale of treasury stock			319,676			664,546	984,222
Purchase of treasury stock						(760,713)	(760,713)
Stock dividends	807,356	124,460	2,175,790		(3,107,607)		(1)
Conversion Class C to Class A
Stockholders' Equity Attributable to Parent, Ending Balance at Jun. 30, 2020	$ 33,115,108	$ 5,102,890	$ 48,917,891	$ 16,894,089	$ 120,126,524	$ (1,542,276)	$ 222,614,226