Comprehensive Income (AOCI Rollforward) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020		Sep. 30, 2019	Dec. 31, 2019	[1]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,822,607,413	$ 1,904,334,235	$ 1,938,087,820	[1]	$ 1,861,751,660
Comprehensive Income	118,800,418	110,636,126	209,960,533		325,974,721
Balance at end of period	1,895,612,299	1,921,328,263	1,895,612,299		1,921,328,263
Accumulated other comprehensive income (loss), end of period	4,447,060		4,447,060			$ (1,289,103)
Accumulated  Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	2,739,244	499,221	(1,289,103)		(1,600,338)
Balance at end of period	4,447,060	(762,505)	4,447,060		(762,505)
Accumulated other comprehensive income (loss), end of period	4,447,060	(762,505)	4,447,060		(762,505)
Foreign currency translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(2,940,052)	(1,851,574)	(2,384,589)		(1,674,887)
Other Comprehensive income (loss) before reclassifications	1,823,667	(1,623,102)	1,268,204		(1,799,789)
Comprehensive Income	1,823,667	(1,623,102)	1,268,204		(1,799,789)
Balance at end of period	(1,116,385)	(3,474,676)	(1,116,385)		(3,474,676)
Unrealized gains (losses) on available-for-sale debt securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	5,679,296	2,350,795	1,095,486		74,549
Other Comprehensive income (loss) before reclassifications	208,503	657,128	5,543,455		3,106,369
Comprehensive Income	(115,851)	361,376	4,467,959		2,637,622
Amounts reclassified from accumulated other comprehensive income	(324,354)	(295,752)	(1,075,496)		(468,747)
Balance at end of period	$ 5,563,445	$ 2,712,171	$ 5,563,445		$ 2,712,171

[1] The condensed consolidated balance sheet at December 31, 2019 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements.