Cash, Cash Equivalents and Marketable Securities - Schedule of Cash, Cash Equivalents and Marketable Securities (Detail) - USD ($)		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Cash Equivalents And Marketable Securities [Line Items]
Cash		$ 2,127,175	$ 979,485
Money market funds		1,230,297	1,043,852
Reverse repurchase agreements		44,000,000	18,000,000
U.S. government agency securities		46,251,444	22,941,293
Available for Sale	[1]	90,251,444	40,941,293
Cash and Cash Equivalents		47,357,472	20,023,337	$ 12,015,061
Current Marketable Securities		46,242,220	22,923,462
Available for Sale [Member]
Cash Cash Equivalents And Marketable Securities [Line Items]
Unrecognized Gain	[1]	0	0
Unrecognized Loss	[1]	(9,224)	(17,831)
Estimated Fair Value	[1]	90,242,220	40,923,462
Cash and Cash Equivalents	[1]	44,000,000	18,000,000
Current Marketable Securities	[1]	46,242,220	22,923,462
Cash [Member]
Cash Cash Equivalents And Marketable Securities [Line Items]
Unrecognized Gain		0	0
Estimated Fair Value		2,127,175	979,485
Cash and Cash Equivalents		2,127,175	979,485
Money Market Funds [Member]
Cash Cash Equivalents And Marketable Securities [Line Items]
Unrecognized Gain		0	0
Estimated Fair Value		1,230,297	1,043,852
Cash and Cash Equivalents		1,230,297	1,043,852
Reverse Repurchase Agreements [Member]
Cash Cash Equivalents And Marketable Securities [Line Items]
Unrecognized Gain		0	0
Estimated Fair Value		44,000,000	18,000,000
Cash and Cash Equivalents		44,000,000	18,000,000
U.S. Government Agencies Securities [Member]
Cash Cash Equivalents And Marketable Securities [Line Items]
Unrecognized Gain		0	0
Unrecognized Loss		(9,224)	(17,831)
Estimated Fair Value		46,242,220	22,923,462
Current Marketable Securities		$ 46,242,220	$ 22,923,462

[1] Available for sale securities are reported at fair value with unrealized gains and losses reported net of taxes, if material, in other comprehensive income.