Carrying Amounts and Fair Values of Company's Financial Instruments (Detail) - USD ($)	Dec. 31, 2018		Dec. 31, 2017
Assets
Assets, Fair Value Disclosure	$ 86,627,847		$ 42,374,500
Fair Value, Inputs, Level 1 [Member]
Assets
Assets, Fair Value Disclosure	86,627,847		42,374,500
Fair Value, Inputs, Level 2 [Member]
Assets
Assets, Fair Value Disclosure	0		0
Money Market Funds [Member]
Assets
Assets, Fair Value Disclosure	85,500,745	[1]	41,231,405
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Assets, Fair Value Disclosure	85,500,745	[1]	41,231,405
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Assets, Fair Value Disclosure	0	[1]	0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Assets, Fair Value Disclosure	0	[1]	0
Marketable securities – certificates of deposit
Assets
Assets, Fair Value Disclosure	1,066,103		1,057,090
Marketable securities – certificates of deposit | Fair Value, Inputs, Level 1 [Member]
Assets
Assets, Fair Value Disclosure	1,066,103		1,057,090
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	60,999		86,005
Marketable securities – equity securities | Fair Value, Inputs, Level 1 [Member]
Assets
Assets, Fair Value Disclosure	60,999		86,005
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

[1] Included in cash and cash equivalents