Comprehensive Income (Reclassification Out of Accumulated Other Comprehensive Income) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Provision for Income Taxes	$ (162,969,497)	$ (145,121,597)	$ (126,721,911)
Amounts Reclassified from Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period	(1,182,844)	3,822,086	10,135,535
Amounts Reclassified from Other Comprehensive Income | Unrealized gains and (losses) on available-for-sale securities
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Realized gain (loss)	320,197	6,960,881	15,593,131
Provision for Income Taxes	(112,069)	(2,436,308)	(5,457,596)
Total reclassifications for the period	208,128	4,524,573	10,135,535
Amounts Reclassified from Other Comprehensive Income | Unrealized gains (losses) on derivatives
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Realized gain (loss)	(2,139,958)	(1,080,750)	0
Provision for Income Taxes	748,986	378,263	0
Total reclassifications for the period	$ (1,390,972)	$ (702,487)	$ 0