Cash, Cash Equivalents and Short-Term Investments (Tables)

6 Months Ended

Jun. 30, 2018

Cash And Cash Equivalents [Abstract]

Schedule of Cash and Cash Equivalents and Short-Term Investments by Significant Investment Category

The following tables show the Company’s cash and cash equivalents and short-term investments by significant investment category as of June 30, 2018 and December 31, 2017:

	June 30, 2018
	Amortized Cost		Gross Unrealized Losses			Estimated Fair Value		Cash and Cash Equivalents		Short-Term Investments
Cash	$	2,472,787	$	—		$	2,472,787	$	2,472,787	$	—
Level 1 (1):
Money market funds		4,766,639		—			4,766,639		4,766,639		—
U.S. treasury securities		2,500,905		(2,297	)		2,498,608		—		2,498,608
Subtotal		7,267,544		(2,297	)		7,265,247		4,766,639		2,498,608
Level 2 (2):
Commercial paper		9,701,381		—			9,701,381		2,246,170		7,455,211
Corporate debt obligations		5,323,767		(2,059	)		5,321,708		773,432		4,548,276
Repurchase agreements		3,000,329		—			3,000,329		3,000,329		—
Asset-backed securities		4,319,154		(3,594	)		4,315,560		—		4,315,560
Subtotal		22,344,631		(5,653	)		22,338,978		6,019,931		16,319,047
Total	$	32,084,962	$	(7,950	)	$	32,077,012	$	13,259,357	$	18,817,655

	December 31, 2017
	Amortized Cost		Gross Unrealized Losses			Estimated Fair Value		Cash and Cash Equivalents		Short-Term Investments
Cash	$	3,040,696	$	—		$	3,040,696	$	3,040,696	$	—
Level 1 (1):
Money market funds		8,234,751		—			8,234,751		8,234,751		—
U.S. treasury securities		2,490,799		(5,540	)		2,485,259		—		2,485,259
Subtotal		10,725,550		(5,540	)		10,720,010		8,234,751		2,485,259
Level 2 (2):
Commercial paper		9,716,093		—			9,716,093		—		9,716,093
Corporate debt obligations		6,829,191		(9,414	)		6,819,777		—		6,819,777
Repurchase agreements		3,000,233		—			3,000,233		3,000,233		—
Asset-backed securities		3,018,276		(1,953	)		3,016,323		750,388		2,265,935
Subtotal		22,563,793		(11,367	)		22,552,426		3,750,621		18,801,805
Total	$	36,330,039	$	(16,907	)	$	36,313,132	$	15,026,068	$	21,287,064

(1) Level 1 fair value estimates are based on quoted prices in active markets for identical assets or liabilities.

(2) Level 2 fair value estimates are based on observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.  

Summary of Short-term Investments with Unrealized Losses

The following table presents the Company’s short-term investments with unrealized losses by investment category and length of time that individual securities have been in a continuous unrealized loss position as of June 30, 2018:

	Less Than 12 Months
Description of Securities	Estimated Fair Value		Unrealized Losses
June 30, 2018
U.S. treasury securities	$	2,498,608	$	(2,297	)
Corporate debt obligations		4,548,276		(1,834	)
Asset-backed securities		4,315,560		(3,594	)
Total	$	11,362,444	$	(7,725	)

Schedule of Contractual Maturities of Short-term Investments

Contractual maturities of short-term investments as of June 30, 2018 are as follows:

	Estimated Fair Value
Due within one year	$	18,817,655
Total	$	18,817,655