Consolidated Statement of Stockholders' Equity - 9 months ended Sep. 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	1,390,065	1,389,022				$ 1,043
Issuance of common stock, shares						104,271
Share-based compensation	10,402,182	10,396,351				$ 5,831
Share-based compensation, shares						583,057
Net income	25,246,971			25,246,971
Cash dividends declared	(6,985,523)			(6,985,523)
Grant of stock options		575,090		(575,090)
Other comprehensive income	5,566,548		5,566,548
Ending balance at Sep. 30, 2016	$ 444,008,811	$ 231,885,764	$ 6,340,292	$ 246,710,728	$ (41,226,357)	$ 241,892	$ 56,492
Ending balance, shares at Sep. 30, 2016						24,189,133	5,649,240