Basis of Presentation and Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
Dec. 31, 2017 USD ($) Segment	Dec. 31, 2016 USD ($)
Class of Stock [Line Items]
Number of segment \| Segment	1
Investment maturity period	Three months or less
Marketable securities maturity period	90 days
Net loss	$ (22,340,589)	$ (18,699,450)
Unrealized gain (loss) on marketable securities	$ (17,960)	8,490
Maximum [Member]
Class of Stock [Line Items]
Minimum maturity period	90 days
Minimum [Member]
Class of Stock [Line Items]
Percentage of investment in the form of government securities and obligations	102.00%
Intellectual Property [Member]
Class of Stock [Line Items]
Intellectual property related expenses	$ 768,000	$ 554,000

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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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