SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Fair Value Measurements (Details) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Fair Value Measurements [Abstract]
Held-to-maturity securities, unrecognized gain	$ 0	$ 0
Held-to-maturity securities, unrecognized (loss)	0	0
Amortized premium included in interest income	(372,000)	(673,000)
Debt Securities, Held-to-maturity [Abstract]
Held-to-maturity securities, current	67,707,143	51,973,971
Held-to-maturity securities, noncurrent	1,099,834	5,745,974
Municipal Bonds [Member]
Debt Securities, Held-to-maturity [Abstract]
Held-to-maturity securities, current	1,295,350	1,002,650
Held-to-maturity securities, noncurrent	0	100,000
Corporate Bonds [Member]
Debt Securities, Held-to-maturity [Abstract]
Held-to-maturity securities, current	61,321,162	48,143,495
Held-to-maturity securities, noncurrent	1,099,834	3,155,575
Certificates of Deposit [Member]
Debt Securities, Held-to-maturity [Abstract]
Held-to-maturity securities, current	5,090,631	2,827,826
Held-to-maturity securities, noncurrent	$ 0	$ 249,019

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Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of investment in debt security measured at amortized cost (held-to-maturity), classified as current.

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Amount of investment in debt security measured at amortized cost (held-to-maturity), classified as noncurrent.

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