Comprehensive Income (AOCI Rollforward) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021		Jun. 30, 2020	Dec. 31, 2020	[1]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,960,980,714	$ 1,834,605,633	$ 1,963,943,128	[1]	$ 1,938,087,820
Net current-period change	2,310,371	2,524,450	(2,586,014)		4,028,347
Balance at end of period	1,916,318,989	1,822,607,413	1,916,318,989		1,822,607,413
Accumulated other comprehensive income, end of period	4,265,038		4,265,038			$ 6,851,052
Accumulated  Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	1,954,667	214,794	6,851,052		(1,289,103)
Net current-period change	2,310,371	2,524,450	(2,586,014)		4,028,347
Balance at end of period	4,265,038	2,739,244	4,265,038		2,739,244
Accumulated other comprehensive income, end of period	4,265,038	2,739,244	4,265,038		2,739,244
Foreign currency translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(83,367)	(3,076,679)	769,045		(2,384,589)
Other Comprehensive income (loss) before reclassifications	963,199	136,627	110,787		(555,463)
Net current-period change	963,199	136,627	110,787		(555,463)
Balance at end of period	879,832	(2,940,052)	879,832		(2,940,052)
Unrealized gains (losses) on available-for-sale debt securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	2,038,034	3,291,473	6,082,007		1,095,486
Other Comprehensive income (loss) before reclassifications	1,610,141	3,109,755	(2,082,477)		5,334,951
Amounts reclassified from accumulated other comprehensive income	(262,969)	(721,932)	(614,324)		(751,141)
Net current-period change	1,347,172	2,387,823	(2,696,801)		4,583,810
Balance at end of period	$ 3,385,206	$ 5,679,296	$ 3,385,206		$ 5,679,296

[1] The condensed consolidated balance sheet at December 31, 2020 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.