Consolidated Statements of Stockholders' Equity - USD ($)	Total	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Class A Common Stock [Member]	Class B Common Stock [Member]
Beginning balance at Dec. 31, 2016	$ 438,615,320	$ 236,851,709	$ (2,254,271)	$ 244,942,913	$ (41,226,357)	$ 244,834	$ 56,492
Beginning balance, shares at Dec. 31, 2016						24,483,377	5,649,240
Issuance of common stock (stock compensation plans)	2,488,333	2,486,762				$ 1,571
Issuance of common stock (stock compensation plans), shares						157,085
Stock-based compensation	15,471,719	15,462,479				$ 9,240
Stock-based compensation, Shares						924,019
Net income (loss)	7,116,100			7,116,100
Cash dividends	(15,041,051)			(15,041,051)
Grant of stock options		600,608		(600,608)
Reclassification of tax effects			(475,687)	475,687
Other comprehensive income (loss)	45,683		45,683
Ending balance at Dec. 31, 2017	448,696,104	255,401,558	(2,684,275)	236,893,041	(41,226,357)	$ 255,645	$ 56,492
Ending balance, shares at Dec. 31, 2017						25,564,481	5,649,240
Issuance of common stock (stock compensation plans)	2,470,969	2,469,220				$ 1,749
Issuance of common stock (stock compensation plans), shares						174,899
Stock-based compensation	2,853,911	2,853,111				$ 800
Stock-based compensation, Shares						79,961
Net income (loss)	(32,760,340)			(32,760,340)
Cash dividends	(15,765,614)			(15,765,614)
Grant of stock options		534,534		(534,534)
Reclassification of equity unrealized gains			(4,918,655)	4,918,655
Other comprehensive income (loss)	(6,625,129)		(6,625,129)
Ending balance at Dec. 31, 2018	398,869,901	261,258,423	(14,228,059)	192,751,208	(41,226,357)	$ 258,194	$ 56,492
Ending balance, shares at Dec. 31, 2018						25,819,341	5,649,240
Issuance of common stock (stock compensation plans)	2,227,198	2,225,527				$ 1,671
Issuance of common stock (stock compensation plans), shares						167,096
Stock-based compensation	4,253,840	4,251,665				$ 2,175
Stock-based compensation, Shares						217,498
Net income (loss)	47,151,744			47,151,744
Cash dividends	(16,219,393)			(16,219,393)
Grant of stock options		415,986		(415,986)
Other comprehensive income (loss)	14,732,229		14,732,229
Ending balance at Dec. 31, 2019	$ 451,015,519	$ 268,151,601	$ 504,170	$ 223,267,573	$ (41,226,357)	$ 262,040	$ 56,492
Ending balance, shares at Dec. 31, 2019						26,203,935	5,649,240