Available-for-Sale Securities and Fair Value Measurements

3 Months Ended

Mar. 31, 2020

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:

	March 31, 2020		December 31, 2019
	(in thousands)
Cash equivalents	$	67,227	$	18,461
Short-term marketable securities	222,838		244,693
Long-term marketable securities	41,690		39,352
Total marketable securities	$	331,755	$	302,506

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

	Fair Value Hierarchy Level	March 31, 2020								December 31, 2019
		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	$	115,877	$	22	$	(300)	$	115,599	$	109,780	$	136	$	(6)	$	109,910
Commercial paper	Level 2	34,191		—		—		34,191		41,237		—		—		41,237
Asset-backed securities	Level 2	39,803		9		(93)		39,719		57,195		63		(5)		57,253
Repurchase agreements	Level 2	—		—		—		—		18,000		—		—		18,000
U.S. treasury securities	Level 1	74,337		682		—		75,019		75,574		71		—		75,645
Money market funds	Level 1	67,227		—		—		67,227		461		—		—		461
Total Marketable securities		$	331,435	$	713	$	(393)	$	331,755	$	302,247	$	270	$	(11)	$	302,506

We estimate the fair value of marketable securities classified as Level 1 using quoted market prices for these or similar 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 March 31, 2020 were not significant and were primarily due to changes in interest rates, and not increased credit risk. Accordingly, we have not recorded an allowance for credit losses associated with these investments.

We do not intend to sell the investments that are currently in an unrealized loss position, and it is highly unlikely that we will be required to sell the investments before recovery of their full amortized cost basis, which will most likely be at maturity

We classified accrued interest on our marketable securities of $1.4 million and $1.0 million as of March 31, 2020 and December 31, 2019, respectively, within prepaid and other current assets on our condensed consolidated balance sheet.

As of March 31, 2020, all our marketable securities had original maturities of less than two years. The weighted-average maturity of our holdings was five months. As of March 31, 2020, our long-term marketable securities had remaining maturities ranging from 13 to 16 months. None of our marketable securities changed from one fair value hierarchy to another during the three months ended