Available-for-Sale Marketable Securities

3 Months Ended

Mar. 31, 2020

Investments Debt And Equity Securities [Abstract]

Available-for-Sale Marketable Securities

3. Available-for-Sale Marketable Securities

As of March 31, 2020 and December 31, 2019, 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 March 31, 2020 and December 31, 2019:

As of March 31, 2020

			Gross Unrealized				Estimated Fair
Type of Security	Amortized Cost		Gains		Losses		Value
U.S. Treasury securities	$	16,065	$	249	$	—	$	16,314
U.S. government agency obligations		17,601		39		(1)		17,639
Corporate bonds		93,681		79		(460)		93,300
Commercial paper		31,949		26		—		31,975
Municipal bonds		3,500		—		—		3,500
Total available-for-sale marketable securities	$	162,796	$	393	$	(461)	$	162,728

As of December 31, 2019

			Gross Unrealized				Estimated Fair
Type of Security	Amortized Cost		Gains		Losses		Value
U.S. Treasury securities	$	16,052	$	31	$	(2)	$	16,081
U.S. government agency obligations		25,803		14		(1)		25,816
Corporate bonds		115,788		125		(23)		115,890
Commercial paper		38,547		27		(1)		38,573
Municipal bonds		3,500		—		—		3,500
Total available-for-sale marketable securities	$	199,690	$	197	$	(27)	$	199,860

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 March 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. government agency obligations	$	4,248	$	(1)	$	—	$	—	$	4,248	$	(1)
Corporate bonds		63,046		(460)		—		—		63,046		(460)
Total	$	67,294	$	(461)	$	—	$	—	$	67,294	$	(461)

As of December 31, 2019

	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	$	3,185	$	(2)	$	—	$	—	$	3,185	$	(2)
U.S. government agency obligations		2,400		(1)		—		—		2,400		(1)
Corporate bonds		28,895		(23)		—		—		28,895		(23)
Commercial paper		4,264		(1)		—		—		4,264		(1)
Total	$	38,744	$	(27)	$	—	$	—	$	38,744	$	(27)

As of March 31, 2020 and December 31, 2019, respectively, 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 for the following categories of securities is as follows:

As of March 31, 2020 and December 31, 2019, the Company held a total of 29 out of 68 positions and 16 out of 81 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 caused by reduced liquidity in this category of debt securities due to the COVID-19 pandemic. The contractual terms of those investments do not permit the issuer to settle the securities at a price less than the amortized cost bases of the investments. The Company does not intend to sell the investments and it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost bases. As of March 31, 2020, the Company held 1 out of 6 positions in an unrealized loss position for its U.S. government agency obligations.

Corporate bonds. The unrealized losses on the Company’s investments in corporate bonds relate to increased volatility and reduced liquidity in the investment grade corporate debt market due to the COVID-19 pandemic. The credit ratings of the corporate bonds in the Company’s portfolio have not been downgraded below investment grade status as a result of the pandemic. The Company expects to recover the entire amortized cost bases of those securities as the pandemic subsides and markets normalize. The Company does not intend to sell its investments in corporate bonds, and it is not more likely than not that the Company will be required to sell those investments before recovery of their amortized cost bases. As of March 31, 2020, the Company held 28 out of 42 positions in an unrealized loss position for its corporate bonds.

The Company classifies its marketable debt securities based on their contractual maturity dates. As of March 31, 2020, the Company’s marketable debt securities mature at various dates through December 2021. The amortized cost and fair values of marketable debt securities by contractual maturity were as follows.

	As of March 31, 2020				As of December 31, 2019
Contractual maturity	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Less than one year	$	103,142	$	103,160	$	136,565	$	136,701
One year to two years		59,654		59,568		63,125		63,159
Total	$	162,796	$	162,728	$	199,690	$	199,860

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 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.

There were no sales of available-for-sale marketable securities during the three months ended March 31, 2020 and 2019, respectively.

As of March 31, 2020 and December 31, 2019, accrued interest receivables on our available-for-sale debt securities were $847 and $971, respectively.