Marketable Securities

12 Months Ended

Dec. 31, 2021

The amortized cost, unrealized gain (loss), and estimated fair value of the Company's investments in securities available for sale consisted of the following:


	December 31, 2021
	Amortized Cost		Unrealized Gain		Unrealized Loss		Estimated Fair Value
Marketable securities
U.S. government securities	$	420,392	$	—	$	(2,107)	$	418,285
Commercial paper	13,878		—		—		13,878
Asset-backed securities	2,003		—		(1)		2,002
Corporate debt securities	18,731		3		(24)		18,710
Total marketable securities	$	455,004	$	3	$	(2,132)	$	452,875


	December 31, 2020
	Amortized Cost		Unrealized Gain		Unrealized Loss		Estimated Fair Value
Marketable securities
U.S. government securities	$	125,823	$	47	$	(6)	$	125,864
Commercial paper	4,991		—		—		4,991
Asset-backed securities	4,294		21		—		4,315
Corporate debt securities	14,683		52		(2)		14,733
Total marketable securities	$	149,791	$	120	$	(8)	$	149,903

The Company had nineteen and six separate marketable securities in unrealized loss positions as of December 31, 2021 and 2020, respectively. The Company did not identify any marketable securities that were other-than-temporarily impaired as of December 31, 2021 and 2020. The Company does not intend to sell any marketable securities that have an unrealized losses at December 31, 2021 and it is not more likely than not that the Company will be required to sell such securities before any anticipated recovery.

The following table summarizes the stated maturities of the Company’s marketable securities:


	December 31, 2021				December 31, 2020
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value

Due within one year	$	64,914	$	64,879	$	149,791	$	149,903
Due after one year through two years	390,090		387,996		—		—
Total	$	455,004	$	452,875	$	149,791	$	149,903