CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) (USD $)	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) [Abstract]
Net income	$ 14,272,517		$ 19,223,735
OTHER COMPREHENSIVE INCOME (LOSS)
Change in unrealized holding gains on investment securities, net of deferred income tax expense of $3,698,356 and $6,473,538	6,868,379		12,022,285
Reclassification adjustment for realized investment gains included in net income, net of income tax (expense) of ($933,755) and ($3,121,415)	(1,734,118)		(5,796,914)
Reclassification adjustment for amounts amortized into net periodic pension and postretirement benefit cost, net of deferred income tax expense of $188,746 and $233,991:
Net actuarial loss	465,606		520,617
Prior service credit	(115,079)		(86,061)
Total reclassification adjustment associated with affiliate's pension and postretirement benefit plans	350,527		434,556
Other comprehensive income	5,484,788	[1]	6,659,927
Total comprehensive income	$ 19,757,305		$ 25,883,662

[1] All amounts are net of tax. Amounts in parentheses indicate debits.