Consolidated Statements of Stockholders' Equity - USD ($)	Total	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Class A Common Stock [Member]	Class B Common Stock [Member]
Beginning balance at Dec. 31, 2015	$ 408,388,568	$ 219,525,301	$ 773,744	$ 229,024,370	$ (41,226,357)	$ 235,018	$ 56,492
Beginning balance, shares at Dec. 31, 2015						23,501,805	5,649,240
Issuance of common stock (stock compensation plans)	2,119,962	2,118,471				$ 1,491
Issuance of common stock (stock compensation plans), shares						149,105
Stock-based compensation	14,530,542	14,522,217				$ 8,325
Stock-based compensation, Shares						832,467
Net income (loss)	30,801,137			30,801,137
Cash dividends	(14,196,874)			(14,196,874)
Grant of stock options		685,720		(685,720)
Other comprehensive income (loss)	(3,028,015)		(3,028,015)
Ending balance at Dec. 31, 2016	438,615,320	236,851,709	(2,254,271)	244,942,913	(41,226,357)	$ 244,834	$ 56,492
Ending 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