Consolidated Statements of Stockholders' Equity - 3 months ended Mar. 31, 2017 - 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, 2016	$ 438,615,320	$ 236,851,709	$ (2,254,271)	$ 244,942,913	$ (41,226,357)	$ 244,834	$ 56,492
Beginning balance, shares at Dec. 31, 2016						24,483,377	5,649,240
Issuance of common stock	412,073	411,798				$ 275
Issuance of common stock, shares						27,512
Share-based compensation	2,237,672	2,236,612				$ 1,060
Share-based compensation, shares						106,009
Net income	5,104,818			5,104,818
Cash dividends declared	(5,756)			(5,756)
Grant of stock options		190,302		(190,302)
Other comprehensive income	346,779		346,779
Ending balance at Mar. 31, 2017	$ 446,710,906	$ 239,690,421	$ (1,907,492)	$ 249,851,673	$ (41,226,357)	$ 246,169	$ 56,492
Ending balance, shares at Mar. 31, 2017						24,616,898	5,649,240