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

12 Months Ended

Dec. 31, 2018

Cash And Cash Equivalents [Abstract]

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

The following table shows the Company’s cash and cash equivalents and short-term investments by significant investment category as of December 31, 2018:

		December 31, 2018
		Amortized Cost				Gross Unrealized Gains				Gross Unrealized Losses				Estimated Fair Value				Cash and Cash Equivalents				Short-Term Investments
Cash		$	3,043,800			$	—			$	—			$	3,043,800			$	3,043,800			$	—
Level 1 (1):
Money market funds			5,481,647				—				—				5,481,647				5,481,647				—
U.S. treasury securities			1,987,794				—				(164	)			1,987,630				—				1,987,630
Subtotal			7,469,441				—				(164	)			7,469,277				5,481,647				1,987,630
Level 2 (2):
Commercial paper			10,639,390				—				—				10,639,390				2,094,983				8,544,407
Corporate debt obligations			5,963,913				—				(6,678	)			5,957,235				—				5,957,235
Repurchase agreements			3,000,226				—				—				3,000,226				3,000,226				—
Asset-backed securities			3,682,413				250				(2,954	)			3,679,709				—				3,679,709
Subtotal			23,285,942				250				(9,632	)			23,276,560				5,095,209				18,181,351
Total		$	33,799,183			$	250			$	(9,796	)		$	33,789,637			$	13,620,656			$	20,168,981

		December 31, 2017
		Amortized Cost				Gross Unrealized Losses				Estimated Fair Value				Cash and Cash Equivalents				Short-Term Investments				Long-Term Marketable Securities
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 December 31, 2018:

		Less Than 12 Months
Description of Securities		Estimated Fair Value				Unrealized Losses
December 31, 2018
U.S. treasury securities		$	1,987,630			$	(164	)
Corporate debt obligations			5,957,235				(6,678	)
Asset-backed securities			3,031,912				(2,954	)
Total		$	10,976,777			$	(9,796	)

Schedule of Contractual Maturities of Short-term Investments

Contractual maturities of short-term investments as of December 31, 2018 are as follows:

		Estimated Fair Value
Due within one year		$	20,168,981
Total		$	20,168,981

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Tabular disclosure of maturities of an entity's investments as well as any other information pertinent to the investments.

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For all investments in an unrealized loss position, including those for which other-than-temporary impairments have not been recognized in earnings (including investments for which a portion of an other-than-temporary impairment has been recognized in other comprehensive income), a tabular disclosure of the aggregate related fair value of investments with unrealized losses and the aggregate amount of unrealized losses (that is, the amount by which amortized cost basis exceeds fair value).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

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