Consolidated Statements Of Stockholders' Equity (USD $)	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Total
Balance at Dec. 31, 2010	$ 1	$ 98,240,109	$ 5,688,705	$ 103,928,815
Balance, shares at Dec. 31, 2010	2,282,596
Net income		5,054,477		5,054,477
Dividends		(450,822)		(450,822)
Shares of common stock repurchased and retired		(5,426,478)		(5,426,478)
Shares of common stock repurchased and retired, shares	(168,516)
Stock options exercised		152,526		152,526
Stock options exercised, shares	7,550
Share-based compensation expense		159,783		159,783
Amortization related to postretirement health benefits			6,296	6,296
Net unrealized gain on investments			423,901	423,901
Balance at Sep. 30, 2011	1	97,729,595	6,118,902	103,848,498
Balance, shares at Sep. 30, 2011	2,121,630
Balance at Dec. 31, 2011	1	99,003,018	7,509,165	106,512,184
Balance, shares at Dec. 31, 2011	2,107,681
Net income		7,939,812		7,939,812
Dividends		(438,431)		(438,431)
Shares of common stock repurchased and retired		(2,804,412)		(2,804,412)
Shares of common stock repurchased and retired, shares	(51,207)
Stock options exercised		152,792		152,792
Stock options exercised, shares	6,130			6,130
Share-based compensation expense		55,857		55,857
Amortization related to postretirement health benefits			4,987	4,987
Net unrealized gain on investments			2,175,915	2,175,915
Balance at Sep. 30, 2012	$ 1	$ 103,908,636	$ 9,690,067	$ 113,598,704
Balance, shares at Sep. 30, 2012	2,062,604