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Carrying Amounts and Fair Values of Company's Financial Instruments (Detail) - USD ($) | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Assets |  |
Assets, Fair Value Disclosure | $ 69,147,538 | $ 86,627,847
Fair Value, Inputs, Level 1 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 69,147,538 | 86,627,847
Fair Value, Inputs, Level 2 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 0 | 0
Fair Value, Inputs, Level 3 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 0 | 0
Money Market Funds [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 68,004,532 | 85,500,745
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 68,004,532 | 85,500,745
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 0 | 0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 0 | 0
Marketable securities – certificates of deposit |  |
Assets |  |
Assets, Fair Value Disclosure | 1,074,280 | 1,066,103
Marketable securities – certificates of deposit | Fair Value, Inputs, Level 1 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 1,074,280 | 1,066,103
Marketable securities – certificates of deposit | Fair Value, Inputs, Level 2 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 0 | 0
Marketable securities – certificates of deposit | Fair Value, Inputs, Level 3 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 0 | 0
Marketable securities – equity securities |  |
Assets |  |
Assets, Fair Value Disclosure | 68,726 | 60,999
Marketable securities – equity securities | Fair Value, Inputs, Level 1 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 68,726 | 60,999
Marketable securities – equity securities | Fair Value, Inputs, Level 2 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | 0 | 0
Marketable securities – equity securities | Fair Value, Inputs, Level 3 [Member] |  |
Assets |  |
Assets, Fair Value Disclosure | $ 0 | $ 0

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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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