Available-for-Sale Marketable Securities

9 Months Ended

Sep. 30, 2021

Investments Debt And Equity Securities [Abstract]

Available-for-Sale Marketable Securities

3. Available-for-Sale Marketable Securities

As of September 30, 2021 and December 31, 2020, the Company’s available-for-sale marketable securities consisted of debt securities issued by the U.S. Treasury, U.S. government-sponsored entities and investment grade institutions as well as municipal bonds.

The following tables summarize the Company’s available-for-sale marketable securities by major type of security as of September 30, 2021 and December 31, 2020:

As of September 30, 2021

			Gross Unrealized				Estimated Fair
Type of Security	Amortized Cost		Gains		Losses		Value
U.S. Treasury securities	$	10,067	$	3	$	—	$	10,070
U.S. government agency obligations		17,046		3		(5)		17,044
Corporate bonds		46,920		17		(23)		46,914
Commercial paper		78,452		6		(4)		78,454
Municipal bonds		17,938		19		(15)		17,942
Total available-for-sale marketable securities	$	170,423	$	48	$	(47)	$	170,424

As of December 31, 2020

			Gross Unrealized				Estimated Fair
Type of Security	Amortized Cost		Gains		Losses		Value
U.S. Treasury securities	$	20,710	$	41	$	(1)	$	20,750
U.S. government agency obligations		22,125		4		(1)		22,128
Corporate bonds		49,080		61		(23)		49,118
Commercial paper		116,139		5		(17)		116,127
Municipal bonds		11,680		12		(8)		11,684
Total available-for-sale marketable securities	$	219,734	$	123	$	(50)	$	219,807

The following tables summarize the fair value and gross unrealized losses of the Company’s available-for-sale marketable securities by investment category and disaggregated by the length of time that individual debt securities have been in a continuous unrealized loss position as of September 30, 2021 and December 31, 2020:

As of September 30, 2021

	Less than 12 Months				12 Months or Greater				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
U.S. government agency obligations	$	9,495	$	(5)	$	—	$	—	$	9,495	$	(5)
Corporate bonds		24,488		(23)		—		—		24,488		(23)
Commercial paper		25,976		(4)		—		—		25,976		(4)
Municipal bonds		7,319		(15)		—		—		7,319		(15)
Total	$	67,278	$	(47)	$	—	$	—	$	67,278	$	(47)

As of December 31, 2020

	Less than 12 Months				12 Months or Greater				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
U.S. Treasury securities	$	12,682	$	(1)	$	—	$	—	$	12,682	$	(1)
U.S. government agency obligations		2,500		(1)		—		—		2,500		(1)
Corporate bonds		23,553		(23)		—		—		23,553		(23)
Commercial paper		68,897		(17)		—		—		68,897		(17)
Municipal bonds		6,259		(8)		—		—		6,259		(8)
Total	$	113,891	$	(50)	$	—	$	—	$	113,891	$	(50)

As of September 30, 2021 and December 31, 2020, no allowance for credit losses were recognized on the Company’s available-for-sale debt securities as no portion of the unrealized losses associated with those securities were due to credit losses. The information that the Company considered in reaching the conclusion that an allowance for credit losses was not necessary is as follows:

As of September 30, 2021 and December 31, 2020, the Company held a total of 26 out of 59 positions and 30 out of 59 positions, respectively, that were in an unrealized loss position, none of which had been in an unrealized loss position for 12 months or greater. Unrealized losses individually and in aggregate were not considered to be material for each respective period. Based on the Company’s review of these securities, the Company believes that the cost basis of its available-for-sale marketable securities is recoverable.

U.S. government agency obligations. The unrealized losses on the Company’s investments in direct obligations of U.S. government agencies were due to changes in interest rates and non-credit related factors. The contractual terms of these investments do not permit the issuer to repay principal at a price less than the amortized cost bases of the investments, which is equivalent to the par value on the maturity date. The Company expects to recover the entire amortized cost bases of these securities on the maturity date. The Company does not intend to sell these investments, and it is not more likely than not that the Company will be required to sell these investments before recovery of their amortized cost bases. The Company held 3 out of 5 positions for its U.S. government agency obligations that were in unrealized loss positions as of September 30, 2021.

Corporate bonds, commercial paper, and municipal bonds. The unrealized losses on the Company’s investments in corporate bonds, commercial paper and municipal bonds were due to changes in interest rates and non-credit related factors. The credit ratings of these investments in the Company’s portfolio have not been downgraded below investment

grade status. The contractual terms of these investments do not permit the issuer to repay principal at a price less than the amortized cost bases of the investments, which is equivalent to the par value on the maturity date. The Company expects to recover the entire amortized cost bases of these securities on the maturity date. The Company does not intend to sell these investments, and it is not more likely than not that the Company will be required to sell these investments, before recovery of their amortized cost bases. The Company held 10 out of 20 positions for its corporate bonds, 7 out of 19 positions for its commercial paper, and 6 out of 12 positions for its municipal bonds, that were in unrealized loss positions as of September 30, 2021.

The Company classifies its marketable debt securities based on their contractual maturity dates. As of September 30, 2021, the Company’s marketable debt securities mature at various dates through September 2024. The amortized cost and fair values of marketable debt securities by contractual maturity were as follows.

	As of September 30, 2021				As of December 31, 2020
Contractual maturity	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Less than one year	$	121,189	$	121,203	$	149,164	$	149,242
One year to three years		49,234		49,221		70,570		70,565
Total	$	170,423	$	170,424	$	219,734	$	219,807

All available-for-sale marketable securities are classified as Marketable securities, current or Marketable securities, non-current depending on the contractual maturity date of the individual available-for-sale security. Other income, net includes interest and dividends, accretion/amortization of discounts/premiums, realized gains and losses on sales of securities and credit loss expense due to declines in the fair value of securities, if any. The cost of securities sold is based on the specific identification method.

During the three and nine months ended September 30, 2021, the Company sold certain shares of its available-for-sale debt securities with a total fair value of $1,000 and $10,029, respectively, which resulted in no realized gains or losses for the three months ended September 30, 2021, and $39 of realized gains for the nine months ended September 30, 2021, respectively. During the three and nine months ended September 30, 2020, the Company sold certain shares of its available-for-sale debt securities with a total fair value of $12,471 and $23,148, respectively, which resulted in realized gains of $66 and $126 for the three and nine months ended September 30, 2020, respectively.

As of September 30, 2021 and December 31, 2020, accrued interest receivables on our available-for-sale debt securities were $318 and $311, respectively.