Accumulated Other Comprehensive Income Balances Of Each Component Of Accumulated Other Comprehensive Income, Net Of Tax (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 11,761,447	$ 11,483,015	$ 12,856,509
Other comprehensive income (loss) before reclassifications	4,968,754	757,647	(1,397,270)
Amounts reclassified from accumulated other comprehensive income	(785,375)	(479,215)	23,776
Other comprehensive income (loss)	4,183,379	278,432	(1,373,494)
Ending balance	15,944,826	11,761,447	11,483,015
Unrealized Gains And Losses On Available-For-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	11,870,647	11,597,741	12,934,497
Other comprehensive income (loss) before reclassifications	4,922,796	758,021	(1,355,316)
Amounts reclassified from accumulated other comprehensive income	(791,061)	(485,115)	18,560
Other comprehensive income (loss)	4,131,735	272,906	(1,336,756)
Ending balance	16,002,382	11,870,647	11,597,741
Postretirement Benefits Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(109,200)	(114,726)	(77,988)
Other comprehensive income (loss) before reclassifications	45,958	(374)	(41,954)
Amounts reclassified from accumulated other comprehensive income	5,686	5,900	5,216
Other comprehensive income (loss)	51,644	5,526	(36,738)
Ending balance	$ (57,556)	$ (109,200)	$ (114,726)