Marketable Securities

12 Months Ended

Dec. 31, 2021

Note 4. Marketable Securities

The following table summarizes the available-for-sale debt securities held at December 31, 2021 and 2020 and (in thousands):


Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2021
U.S. treasury securities	$	186,700	$	—	$	(45	)	$	186,655
US government agency securities		79,657		—		(125	)		79,532
Corporate securities		253,929		1		(488	)		253,442
Total	$	520,286	$	1	$	(658	)	$	519,629


Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2020
U.S. treasury securities	$	324,917	$	—	$	(53	)	$	324,864
Corporate securities		102,946		—		(81	)		102,865
Total	$	427,863	$	—	$	(134	)	$	427,729

As of December 31, 2021, the Company held 113 securities that had been in an unrealized loss position for less than 12 months with an aggregate fair value of $515.4 million. As of December 31, 2020, the Company held 65 securities that had been in an unrealized loss position for less than 12 months with an aggregate fair value of $392.2 million

As of December 31, 2021, the Company had 79 securities with a fair value of $394.4 million with a contractual maturity of less than 12 months and 37 securities with a fair value of $125.2 million with a contractual maturity of greater than 12 months. As of December 31, 2020, the Company had 48 securities with a fair value of $295.6 million with a contractual maturity of less than 12 months and 25 securities with a fair value of $162.5 million with a contractual maturity of greater than 12 months. During the year ending December 31, 2020, the Company sold one security prior to maturity which resulted in an immaterial realized gain on the sale.

The Company evaluates securities for other-than-temporary impairments based on quantitative and qualitative factors, and considered the decline in market value for the 113 securities in an unrealized loss position as of December 31, 2021, to be primarily attributable to the then current economic and market conditions. The Company neither intends to sell these investments nor concludes that it is more-likely-than-not that the Company will have to sell them before recovery of their carrying values. The Company also believe that it will be able to collect both principal and interest amounts due to it at maturity.