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Investments (Schedule of Amortized Cost, Unrealized Gains And Losses, And Market Value of Investment Securities) (Details) - USD ($) | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Cost | $ 301,641,575 | $ 303,467,531
Unrealized Gains | 1,169,438 | 440,807
Unrealized Losses | (69,283) | (366,257)
Market Value | 302,741,730 | 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 | 21,101,631 | 9,186,586
Unrealized Gains | 9,901 | 0
Unrealized Losses | (1,664) | (10,359)
Market Value | 21,109,868 | 9,176,227
Short-Term Investments | Corporate Bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 5,979,056 | 6,981,305
Unrealized Gains | 4,095 | 0
Unrealized Losses | (463) | (13,605)
Market Value | 5,982,688 | 6,967,700
Short-Term Investments | Other |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 2,921,282 | 2,219,688
Unrealized Gains | 0 | 0
Unrealized Losses | 0 | 0
Market Value | 2,921,282 | 2,219,688
Long-Term Investments | Government Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 34,316,447 | 56,280,552
Unrealized Gains | 218,059 | 205,553
Unrealized Losses | 0 | (2,385)
Market Value | 34,534,506 | 56,483,720
Long-Term Investments | Corporate Bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 66,172,642 | 60,659,498
Unrealized Gains | 504,809 | 50,340
Unrealized Losses | (67,156) | (339,908)
Market Value | 66,610,295 | 60,369,930
Long-Term Investments | Municipal Bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Cost | 20,851,133 | 17,840,518
Unrealized Gains | 432,574 | 184,914
Unrealized Losses | 0 | 0
Market Value | $ 21,283,707 | $ 18,025,432

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- 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=82897076&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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