Consolidated Statements Of Stockholders' Equity (USD $)	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income
Balance, beginning of year at Dec. 31, 2011	$ 106,512,184	$ 1	$ 99,003,018	$ 7,509,165
Balance, beginning of year, shares at Dec. 31, 2011		2,107,681
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to the Company	4,781,627		4,781,627
Dividends ($0.14 per share)	(294,048)		(294,048)
Shares of common stock repurchased and retired (in shares)		(14,502)
Shares of common stock repurchased and retired	(626,885)		(626,885)
Stock options and stock appreciation rights exercised (in shares)		6,130
Stock options and stock appreciation rights exercised	152,792		152,792
Share-based compensation expense	36,947		36,947
Amortization related to postretirement health benefits	3,325			3,325
Net unrealized gain on investments	835,326			835,326
Balance, end of year at Jun. 30, 2012	111,401,268	1	103,053,451	8,347,816
Balance, end of year, shares at Jun. 30, 2012		2,099,309
Balance, beginning of year at Dec. 31, 2012	114,638,890	1	105,820,459	8,818,430
Balance, beginning of year, shares at Dec. 31, 2012		2,043,359
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to the Company	7,382,405		7,382,405
Dividends ($0.14 per share)	(329,569)		(329,569)
Shares of common stock repurchased and retired (in shares)		(19,460)
Shares of common stock repurchased and retired	(1,378,131)		(1,378,131)
Stock options and stock appreciation rights exercised (in shares)		49,749
Stock options and stock appreciation rights exercised	68,032		68,032
Share-based compensation expense	40,092		40,092
Amortization related to postretirement health benefits	1,575			1,575
Net unrealized gain on investments	440,996			440,996
Income tax benefit from share-based compensation	935,563		935,563
Balance, end of year at Jun. 30, 2013	$ 121,799,853	$ 1	$ 112,538,851	$ 9,261,001
Balance, end of year, shares at Jun. 30, 2013		2,073,648