Fair Value Instruments - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Asset included in:
Investments available-for-sale at fair value	$ 18,056,673	$ 22,681,049
U.S. Government Obligations
Asset included in:
Investments available-for-sale at fair value	2,572,596	6,031,515
Corporate Debt Securities
Asset included in:
Investments available-for-sale at fair value	15,484,077	16,649,534
Fair Value, Measurements, Recurring
Asset included in:
Financial Assets	24,782,710	30,602,704
Fair Value, Measurements, Recurring | Money Market Securities
Asset included in:
Cash and cash equivalents	6,726,037	7,921,655
Fair Value, Measurements, Recurring | U.S. Government Obligations
Asset included in:
Investments available-for-sale at fair value	2,572,596	6,031,515
Fair Value, Measurements, Recurring | Corporate Debt Securities
Asset included in:
Investments available-for-sale at fair value	15,484,077	16,649,534
Fair Value, Measurements, Recurring | Level 1
Asset included in:
Financial Assets	9,298,633	12,954,770
Fair Value, Measurements, Recurring | Level 1 | Money Market Securities
Asset included in:
Cash and cash equivalents	6,726,037	6,923,255
Fair Value, Measurements, Recurring | Level 1 | U.S. Government Obligations
Asset included in:
Investments available-for-sale at fair value	2,572,596	6,031,515
Fair Value, Measurements, Recurring | Level 2
Asset included in:
Financial Assets	15,484,077	17,647,934
Fair Value, Measurements, Recurring | Level 2 | Money Market Securities
Asset included in:
Cash and cash equivalents		998,400
Fair Value, Measurements, Recurring | Level 2 | Corporate Debt Securities
Asset included in:
Investments available-for-sale at fair value	$ 15,484,077	$ 16,649,534