Available-for-Sale Securities and Fair Value Measurements

9 Months Ended

Sep. 30, 2021

Available For Sale Securities And Fair Value Measurements [Abstract]

Available-for-Sale Securities and Fair Value Measurements

Available-for-Sale Securities and Fair Value Measurements

The available-for-sale securities in our Condensed Consolidated Balance Sheets are as follows:

	September 30, 2021		December 31, 2020
	(in thousands)
Cash equivalents	$	73,180	$	50,524
Short-term marketable securities	266,643		364,506
Long-term marketable securities	133,845		36,196
Total marketable securities	$	473,668	$	451,226

The following table presents our available-for-sale securities grouped by asset type:

	Fair Value Hierarchy Level	September 30, 2021								December 31, 2020
		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
		(in thousands)
Corporate bonds	Level 2	$	135,204	$	15	$	(37)	$	135,182	$	96,999	$	74	$	(9)	$	97,064
Commercial paper	Level 2	127,395		—		—		127,395		139,791		—		—		139,791
Asset-backed securities	Level 2	63,220		6		(49)		63,177		39,243		15		(1)		39,257
U.S. treasury securities	Level 1	74,726		9		(1)		74,734		124,461		131		(2)		124,590
Money market funds	Level 1	73,180		—		—		73,180		50,524		—		—		50,524
Total marketable securities		$	473,725	$	30	$	(87)	$	473,668	$	451,018	$	220	$	(12)	$	451,226

We estimate the fair value of marketable securities classified as Level 1 using quoted market prices for these or identical investments obtained from a commercial pricing service. We estimate the fair value of marketable securities classified as Level 2 using inputs that may include benchmark yields, reported trades, broker/dealer quotes and issuer spreads.

We periodically review our debt securities to determine if any of our investments is impaired due to credit-related or other issues. If the fair value of our investment in any debt security is less than our amortized cost basis, we determine whether an allowance for credit losses is appropriate by assessing quantitative and subjective factors including, but not limited to, the nature of security, changes in credit ratings, analyst reports concerning the security’s issuer and industry, interest rate fluctuations and general market conditions.

Unrealized losses on our available-for-sale debt securities as of September 30, 2021 were not material. Accordingly, we have not recorded an allowance for credit losses associated with these investments.

We do not intend to sell investments that currently have unrealized losses and it is highly unlikely that we will sell any investment before recovery of its amortized cost basis, which may be at maturity.

We classified accrued interest on our marketable securities of $1.4 million and $1.3 million as of September 30, 2021 and December 31, 2020, respectively, as prepaid and other current assets on our condensed consolidated balance sheets.

As of September 30, 2021, all our marketable securities had original maturities of less than two years. The weighted-average maturity of our holdings was eight months. As of September 30, 2021, our long-term marketable securities had remaining maturities ranging from 13 to 22 months. None of our marketable securities changed from one fair value hierarchy to another during the three and nine months ended September 30, 2021.