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, December 31, (in thousands) Cash equivalents $ 24,266 $ 45,088 Short-term marketable securities 283,665 145,918 Long-term marketable securities 22,566 112,277 Total marketable securities $ 330,497 $ 303,283 The following table presents our available-for-sale securities grouped by asset type: Fair Value March 31, 2022 December 31, 2021 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 $ 147,177 $ 4 $ (1,023) $ 146,158 $ 125,370 $ 3 $ (276) $ 125,097 Commercial paper Level 2 56,751 — — 56,751 30,963 — — 30,963 Asset-backed securities Level 2 29,372 — (110) 29,262 57,801 — (67) 57,734 U.S. Treasury securities Level 1 74,363 — (303) 74,060 44,473 — (72) 44,401 Money market funds Level 1 24,266 — — 24,266 45,088 — — 45,088 Total marketable securities $ 331,929 $ 4 $ (1,436) $ 330,497 $ 303,695 $ 3 $ (415) $ 303,283 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. As of March 31, 2022 and December 31, 2021, unrealized losses on our available-for-sale debt securities were $1.4 million and $0.4 million, respectively. All of our investments, including those with unrealized losses, are not impaired. Unrealized losses on our investments are due to interest rate fluctuations. 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. Accordingly, we have not recorded an allowance for credit losses associated with these investments. We classified accrued interest on our marketable securities of $1.0 million and $1.4 million as of March 31, 2022 and December 31, 2021, respectively, as prepaid and other current assets on our condensed consolidated balance sheets. |