Consolidated Statements Of Stockholders' Equity - USD ($)	Total	Common stocks	Retained Earnings	Accumulated Other Comprehensive Income	Noncontrolling Interest [Member]
Balance, beginning of year at Dec. 31, 2014	$ 137,563,706	$ 1	$ 124,707,196	$ 12,856,509	$ 0
Balance, beginning of year, shares at Dec. 31, 2014		2,023,270
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to the Company	12,533,905		12,533,905
Dividends	(789,907)		(789,907)
Shares of common stock repurchased and retired (in shares)		(75,665)
Shares of common stock repurchased and retired	(5,483,953)		(5,483,953)
Stock options and stock appreciation rights exercised (in shares)		2,192
Stock options and stock appreciation rights exercised	54,988		54,988
Share-based compensation expense	137,762		137,762
Amortization related to postretirement health benefits	5,216			5,216
Accumulated postretirement benefit obligation adjustment	(41,954)			(41,954)
Net unrealized gain (loss) on investments	(1,336,756)			(1,336,756)
Net effect of changes in ownership	127,050				127,050
Subsidiary return of capital	(35,000)				(35,000)
Net Income (Loss) Attributable to Noncontrolling Interest	15,148				15,148
Income tax benefit from share-based compensation	26,875		26,875
Balance, end of year at Dec. 31, 2015	142,777,080	$ 1	131,186,866	11,483,015	107,198
Balance, end of year, shares at Dec. 31, 2015		1,949,797
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to the Company	19,523,118		19,523,118
Dividends	(1,370,390)		(1,370,390)
Shares of common stock repurchased and retired (in shares)		(66,803)
Shares of common stock repurchased and retired	(6,219,670)		(6,219,670)
Stock options and stock appreciation rights exercised (in shares)		1,289
Stock options and stock appreciation rights exercised	(200)		(200)
Share-based compensation expense	132,098		132,098
Amortization related to postretirement health benefits	5,900			5,900
Accumulated postretirement benefit obligation adjustment	(374)			(374)
Net unrealized gain (loss) on investments	272,906			272,906
Purchase of noncontrolling interest of subsidiary	(8,647)				(8,647)
Additional paid-in capital from purchase of noncontrolling interest of subsidiary	(494)		(494)
Subsidiary return of capital	0
Net Income (Loss) Attributable to Noncontrolling Interest	(7,666)				(7,666)
Income tax benefit from share-based compensation	32,293		32,293
Balance, end of year at Dec. 31, 2016	155,135,954	$ 1	143,283,621	11,761,447	90,885
Balance, end of year, shares at Dec. 31, 2016		1,884,283
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to the Company	25,706,502		25,706,502
Dividends	(7,073,210)		(7,073,210)
Shares of common stock repurchased and retired (in shares)		(1,333)
Shares of common stock repurchased and retired	(244,831)		(244,831)
Stock options and stock appreciation rights exercised (in shares)		3,043
Stock options and stock appreciation rights exercised	(737)		(737)
Share-based compensation expense	219,315		219,315
Amortization related to postretirement health benefits	5,686			5,686
Accumulated postretirement benefit obligation adjustment	45,958			45,958
Net unrealized gain (loss) on investments	4,131,735			4,131,735
Subsidiary return of capital	0
Net Income (Loss) Attributable to Noncontrolling Interest	(5,932)				(5,932)
Balance, end of year at Dec. 31, 2017	$ 177,920,440	$ 1	$ 161,890,660	$ 15,944,826	$ 84,953
Balance, end of year, shares at Dec. 31, 2017		1,885,993