Comprehensive Income (Reclassification Out of Accumulated Other Comprehensive Income) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Provision for income taxes									$ (64,249,308)	$ (75,731,395)	$ (84,163,850)
Total reclassifications for the period	$ 143,339,000	$ 117,093,000	$ (2,374,000)	$ 89,506,000	$ 99,547,000	$ 111,898,000	$ 108,959,000	$ 104,280,000	347,563,621	424,683,939	437,883,097
Amounts Reclassified from Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period									1,657,938	382,584	1,682,208
Amounts Reclassified from Other Comprehensive Income | Unrealized gains on available-for-sale debt securities
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Realized gain (loss)									2,098,656	484,283	2,006,235
Provision for income taxes									(440,718)	(101,699)	(421,309)
Total reclassifications for the period									1,657,938	382,584	1,584,926
Amounts Reclassified from Other Comprehensive Income | Unrealized gains (losses) on derivatives:
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Realized gain (loss)									0	0	(123,142)
Provision for income taxes									0	0	(25,860)
Total reclassifications for the period									$ 0	$ 0	$ 97,282