Fair Value of Financial Assets and Liabilities

12 Months Ended

Dec. 31, 2020

Fair Value of Financial Assets and Liabilities

Fair Value of Financial Assets and Liabilities

3.           Fair Value of Financial Assets and Liabilities

The following tables present information about the Company’s financial instruments measured at fair value on a recurring basis and indicate the level of the fair value hierarchy used to determine such fair values:

	Fair Value Measurements
	as of December 31, 2020 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Restricted cash — money market funds	$	210	$	—	$	—	$	210
Cash equivalents — money market funds		22,942		—		—		22,942
Cash equivalents — U.S. Treasury notes		—		72,695		—		72,695
Short-term investments — U.S. Treasury notes		—		209,444		—		209,444
	$	23,152	$	282,139	$	—	$	305,291

	Fair Value Measurements
	as of December 31, 2019 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Restricted cash — money market funds	$	210	$	—	$	—	$	210
Cash equivalents — money market funds		25,207		—		—		25,207
Cash equivalents — U.S. Treasury notes		—		10,192		—		10,192
Short-term investments — U.S. Treasury notes		—		186,452		—		186,452
	$	25,417	$	196,644	$	—	$	222,061

During the years ended December 31, 2020 and 2019 there were no transfers between Level 1, Level 2 and Level 3. The money market funds were valued using quoted prices in active markets, which represent a Level 1 measurement in the fair value hierarchy. The Company's cash equivalents and short-term investments as of December 31, 2020 and 2019 included U.S. Treasury notes, which are not traded on a daily basis and, therefore, represent a Level 2 measurement in the fair value hierarchy at each period end.

Cash equivalents and short-term investments as of December 31, 2020 and 2019 consisted of U.S. Treasury notes which investments were each due within six months of such date.

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
December 31, 2020
Cash equivalents — U.S. Treasury notes	$	72,694	$	1	$	—	$	72,695
Short-term investments — U.S. Treasury notes		209,459		4		(19)		209,444
	$	282,153	$	5	$	(19)	$	282,139

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
December 31, 2019
Cash equivalents — U.S. Treasury notes	$	10,191	$	1	$	—	$	10,192
Short-term investments — U.S. Treasury notes		186,415		44		(7)		186,452
	$	196,606	$	45	$	(7)	$	196,644

As of December 31, 2020, the Company held 17 securities that were in an unrealized loss position. The aggregate fair value of securities held by the Company in an unrealized loss position was $107,753 at December 31, 2020. As of December 31, 2019, the Company held seven securities that were in an unrealized loss position. The aggregate fair value of securities held by the Company in an unrealized loss position was $43,107 at December 31, 2019. As of both December 31, 2020 and 2019, these securities were held by the Company in an unrealized loss position for

less than 12 months. The Company determined that there was no material change in the credit risk of these securities. As a result, the Company determined it did not hold any investments with an other-than-temporary impairment as of December 31, 2020 and 2019.