Comprehensive Income (Reclassification Out of Accumulated Other Comprehensive Income) (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Provision for Income Taxes	$ (25,031,542)		$ (19,913,176)		$ (45,354,887)		$ (42,355,915)
Amounts Reclassified from Other Comprehensive Income [Member] | Unrealized gains(losses) on available-for-sale securities [Member]
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Realized gain (loss) on sale of securities	5,030,124	[1]	2,741,335	[1]	7,852,331	[1]	4,235,900	[1]
Provision for Income Taxes	(1,760,543)	[1]	(959,467)	[1]	(2,748,316)	[1]	(1,482,565)	[1]
Total reclassifications for the period	$ 3,269,581	[1]	$ 1,781,868	[1]	$ 5,104,015	[1]	$ 2,753,335	[1]

[1] Amounts in parentheses indicate debits.