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Investments (Schedule of Amortized Cost, Unrealized Gains and Losses, and Market Value of Investment Securities) (Details) - USD ($) | Sep. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Cost | $ 298,869,584 | $ 303,467,531
Unrealized Gains | 2,730,098 | 440,807
Unrealized Losses | (17,927) | (366,257)
Market Value | 301,581,755 | 303,542,081
Short-Term Investments | Certificates of Deposit |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 150,299,384 | 150,299,384
Unrealized Gains | 0 | 0
Unrealized Losses | 0 | 0
Market Value | 150,299,384 | 150,299,384
Short-Term Investments | Government Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 38,067,382 | 9,186,586
Unrealized Gains | 97,271 | 0
Unrealized Losses | (1,300) | (10,359)
Market Value | 38,163,353 | 9,176,227
Short-Term Investments | Corporate Bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 15,955,794 | 6,981,305
Unrealized Gains | 94,766 | 0
Unrealized Losses | 0 | (13,605)
Market Value | 16,050,560 | 6,967,700
Short-Term Investments | Other |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 971,726 | 2,219,688
Unrealized Gains | 0 | 0
Unrealized Losses | 0 | 0
Market Value | 971,726 | 2,219,688
Short-Term Investments | Municipal Bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 1,673,133 |
Unrealized Gains | 13,163 |
Unrealized Losses | (15,032) |
Market Value | 1,671,264 |
Long-Term Investments | Government Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 11,539,947 | 56,280,552
Unrealized Gains | 97,563 | 205,553
Unrealized Losses | 0 | (2,385)
Market Value | 11,637,510 | 56,483,720
Long-Term Investments | Corporate Bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 41,191,483 | 60,659,498
Unrealized Gains | 1,130,771 | 50,340
Unrealized Losses | (1,595) | (339,908)
Market Value | 42,320,659 | 60,369,930
Long-Term Investments | Municipal Bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 39,170,735 | 17,840,518
Unrealized Gains | 1,296,564 | 184,914
Unrealized Losses | 0 | 0
Market Value | $ 40,467,299 | $ 18,025,432

X
- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
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