Investments (Schedule of Assets or Liabilities, Recurring Fair Value Measurements) (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash & Cash Equivalents	$ 343,811,484	$ 296,321,622
Market Value	232,479,290	271,275,758
Investments and Cash	576,290,774	567,597,380
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash & Cash Equivalents	343,811,484	296,321,622
Investments and Cash	351,829,702	352,610,965
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash & Cash Equivalents	0	0
Investments and Cash	224,461,072	214,986,415
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash & Cash Equivalents	0	0
Investments and Cash	0	0
Short-Term Investments | Certificate of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	1,023,558	50,099,795
Short-Term Investments | Certificate of Deposit | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	1,023,558	50,099,795
Short-Term Investments | Certificate of Deposit | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Short-Term Investments | Certificate of Deposit | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Short-Term Investments | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	18,465,053	29,219,685
Short-Term Investments | Corporate Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Short-Term Investments | Corporate Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	18,465,053	29,219,685
Short-Term Investments | Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Short-Term Investments | Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	43,412,712	58,432,823
Short-Term Investments | Government Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Short-Term Investments | Government Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	43,412,712	58,432,823
Short-Term Investments | Government Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Short-Term Investments | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	4,292,331
Short-Term Investments | Municipal Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0
Short-Term Investments | Municipal Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	4,292,331
Short-Term Investments | Municipal Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0
Short-Term Investments | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	2,821,510	2,631,750
Short-Term Investments | Other | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	2,821,510	2,631,750
Short-Term Investments | Other | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Short-Term Investments | Other | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Long-Term Investments | Certificate of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	4,173,150	3,557,798
Long-Term Investments | Certificate of Deposit | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	4,173,150	3,557,798
Long-Term Investments | Certificate of Deposit | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0
Long-Term Investments | Certificate of Deposit | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Long-Term Investments | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	21,101,912	22,815,998
Long-Term Investments | Corporate Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Long-Term Investments | Corporate Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	21,101,912	22,815,998
Long-Term Investments | Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Long-Term Investments | Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	617,226	6,088,190
Long-Term Investments | Government Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Long-Term Investments | Government Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	617,226	6,088,190
Long-Term Investments | Government Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Long-Term Investments | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	94,430,839	72,638,690
Long-Term Investments | Municipal Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Long-Term Investments | Municipal Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	94,430,839	72,638,690
Long-Term Investments | Municipal Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Long-Term Investments | Asset Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	42,140,999	25,791,029
Long-Term Investments | Asset Backed Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	0	0
Long-Term Investments | Asset Backed Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	42,140,999	25,791,029
Long-Term Investments | Asset Backed Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market Value	$ 0	$ 0