Consolidated Statement of Stockholders' Equity - 6 months ended Jun. 30, 2016 - USD ($)	Total	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income [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	1,124,816	1,123,997				$ 819
Issuance of common stock, shares						81,853
Share-based compensation	6,010,833	6,007,698				$ 3,135
Share-based compensation, shares						313,549
Net income	20,433,567			20,433,567
Cash dividends declared	(3,426,033)			(3,426,033)
Grant of stock options		417,136		(417,136)
Other comprehensive income	7,334,863		7,334,863
Ending balance at Jun. 30, 2016	$ 439,866,614	$ 227,074,132	$ 8,108,607	$ 245,614,768	$ (41,226,357)	$ 238,972	$ 56,492
Ending balance, shares at Jun. 30, 2016						23,897,207	5,649,240