Consolidated Statement 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, 2013	$ 396,877,111	$ 189,116,410	$ (2,312,890)	$ 222,888,887	$ (13,089,656)	$ 217,868	$ 56,492
Beginning balance, shares at Dec. 31, 2013						21,786,765	5,649,240
Issuance of common stock (stock compensation plans)	8,069,704	8,065,021				4,683
Issuance of common stock (stock compensation plans), shares						468,266
Net income	10,052,967			10,052,967
Cash dividends declared	(6,820,219)			(6,820,219)
Grant of stock options		330,637		(330,637)
Tax benefit on exercise of stock options	241,391	241,391
Repurchase of treasury shares	(12,026)				(12,026)
Other comprehensive income (loss)	6,534,985		6,534,985
Ending balance at Sep. 30, 2014	$ 414,943,913	$ 197,753,459	$ 4,222,095	$ 225,790,998	$ (13,101,682)	$ 222,551	$ 56,492
Ending balance, shares at Sep. 30, 2014						22,255,031	5,649,240