Investments (Schedule of Amortized Cost, Unrealized Gains and Losses, and Market Value of Investment Securities) (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Cost	$ 225,290,306	$ 269,889,067
Unrealized Gains	7,244,469	1,974,255
Unrealized Losses	(55,485)	(587,564)
Market Value	232,479,290	271,275,758
Short-Term Investments | Certificate of Deposit
Debt Securities, Available-for-sale [Line Items]
Cost	1,000,000	50,099,795
Unrealized Gains	23,558	0
Unrealized Losses	0	0
Market Value	1,023,558	50,099,795
Short-Term Investments | Corporate Bonds
Debt Securities, Available-for-sale [Line Items]
Cost	18,328,367	29,025,624
Unrealized Gains	138,975	194,061
Unrealized Losses	(2,289)	0
Market Value	18,465,053	29,219,685
Short-Term Investments | Government Securities
Debt Securities, Available-for-sale [Line Items]
Cost	43,146,665	58,343,911
Unrealized Gains	266,047	99,917
Unrealized Losses	0	(11,005)
Market Value	43,412,712	58,432,823
Short-Term Investments | Municipal Bonds
Debt Securities, Available-for-sale [Line Items]
Cost	4,256,184
Unrealized Gains	36,147
Unrealized Losses	0
Market Value	4,292,331
Short-Term Investments | Other
Debt Securities, Available-for-sale [Line Items]
Cost	2,821,510	2,631,750
Unrealized Gains	0	0
Unrealized Losses	0	0
Market Value	2,821,510	2,631,750
Long-Term Investments | Certificate of Deposit
Debt Securities, Available-for-sale [Line Items]
Cost	4,006,912	3,500,000
Unrealized Gains	166,238	58,808
Unrealized Losses	0	(1,010)
Market Value	4,173,150	3,557,798
Long-Term Investments | Corporate Bonds
Debt Securities, Available-for-sale [Line Items]
Cost	20,230,114	22,306,130
Unrealized Gains	871,798	509,868
Unrealized Losses	0	0
Market Value	21,101,912	22,815,998
Long-Term Investments | Government Securities
Debt Securities, Available-for-sale [Line Items]
Cost	614,995	6,012,705
Unrealized Gains	2,231	75,485
Unrealized Losses	0	0
Market Value	617,226	6,088,190
Long-Term Investments | Municipal Bonds
Debt Securities, Available-for-sale [Line Items]
Cost	89,744,967	71,997,996
Unrealized Gains	4,707,257	1,036,116
Unrealized Losses	(21,385)	(395,422)
Market Value	94,430,839	72,638,690
Long-Term Investments | Asset Backed Securities
Debt Securities, Available-for-sale [Line Items]
Cost	41,140,592	25,971,156
Unrealized Gains	1,032,218	0
Unrealized Losses	(31,811)	(180,127)
Market Value	$ 42,140,999	$ 25,791,029