Comprehensive Income (AOCI Rollforward) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020		Mar. 31, 2019	Dec. 31, 2019	[1]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,938,087,820	[1]	$ 1,861,751,660
Net current-period change	91,009,698		105,605,015
Balance at end of period	1,834,605,633		1,857,074,748
Accumulated other comprehensive gain (loss), end of period	214,794			$ (1,289,103)
Accumulated  Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(1,289,103)		(1,600,338)
Balance at end of period	214,794		(275,734)
Accumulated other comprehensive gain (loss), end of period	214,794		(275,734)
Foreign currency translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(2,384,589)		(1,674,887)
Other Comprehensive (loss) income before reclassifications	(692,090)		298,999
Net current-period change	(692,090)		298,999
Balance at end of period	(3,076,679)		(1,375,888)
Unrealized gains (losses) on available-for-sale debt securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	1,095,486		74,549
Other Comprehensive (loss) income before reclassifications	2,225,196		1,095,581
Amounts reclassified from accumulated other comprehensive income	(29,209)		(69,976)
Net current-period change	2,195,987		1,025,605
Balance at end of period	$ 3,291,473		$ 1,100,154

[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.