Consolidated Statement of Stockholders' Equity - 6 months ended Jun. 30, 2018 - USD ($)	Total	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Class A Common Stock [Member]	Class B Common Stock [Member]
Beginning balance at Dec. 31, 2017	$ 448,696,104	$ 255,401,558	$ (2,684,275)	$ 236,893,041	$ (41,226,357)	$ 255,645	$ 56,492
Beginning balance, shares at Dec. 31, 2017						25,564,481	5,649,240
Issuance of common stock	1,383,383	1,382,457				$ 926
Issuance of common stock, shares						92,592
Share-based compensation	1,561,122	1,560,800				$ 322
Share-based compensation, shares						32,176
Net (loss) income	(18,967,933)			(18,967,933)
Cash dividends declared	(3,938,606)			(3,938,606)
Grant of stock options		321,100		(321,100)
Reclassification of equity unrealized gains			(4,918,655)	4,918,655
Other comprehensive (loss) income	(9,064,031)		(9,064,031)
Ending balance at Jun. 30, 2018	$ 419,670,039	$ 258,665,915	$ (16,666,961)	$ 218,584,057	$ (41,226,357)	$ 256,893	$ 56,492
Ending balance, shares at Jun. 30, 2018						25,689,249	5,649,240