Comprehensive Income (AOCI Rollforward) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020		Jun. 30, 2019	Dec. 31, 2019	[1]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,834,605,633	$ 1,857,074,748	$ 1,938,087,820	[1]	$ 1,861,751,660
Comprehensive Income	150,417	109,733,580	91,160,115		215,338,595
Balance at end of period	1,822,607,413	1,904,334,236	1,822,607,413		1,904,334,236
Accumulated other comprehensive income, end of period	2,739,244		2,739,244			$ (1,289,103)
Accumulated  Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	214,794	(275,734)	(1,289,103)		(1,600,338)
Balance at end of period	2,739,244	499,221	2,739,244		499,221
Accumulated other comprehensive income, end of period	2,739,244	499,221	2,739,244		499,221
Foreign currency translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(3,076,679)	(1,375,888)	(2,384,589)		(1,674,887)
Other Comprehensive (loss) income before reclassifications	136,627	(475,686)	(555,463)		(176,687)
Comprehensive Income	136,627	(475,686)	(555,463)		(176,687)
Balance at end of period	(2,940,052)	(1,851,574)	(2,940,052)		(1,851,574)
Unrealized gains (losses) on available-for-sale debt securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	3,291,473	1,100,154	1,095,486		74,549
Other Comprehensive (loss) income before reclassifications	3,109,755	1,353,661	5,334,951		2,449,241
Comprehensive Income	2,387,823	1,250,641	4,583,810		2,276,246
Amounts reclassified from accumulated other comprehensive income	(721,932)	(103,020)	(751,141)		(172,995)
Balance at end of period	$ 5,679,296	$ 2,350,795	$ 5,679,296		$ 2,350,795

[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.