Investment Securities and Fair Value Measurements | Investment Securities and Fair Value Measurements Investment Securities Investment securities classified as available-for-sale consisted of the following as of June 30, 2022 and December 31, 2021 (in thousands): June 30, 2022 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Corporate bonds $ 19,464 $ — $ (60) $ 19,404 Agency securities 19,752 — (443) 19,309 Treasury securities 88,126 — (1,505) 86,621 Total available-for-sale investment securities $ 127,342 $ — $ (2,008) $ 125,334 December 31, 2021 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Corporate bonds $ 29,080 $ — $ (11) $ 29,069 Agency securities 19,753 — (27) 19,726 Treasury securities 77,108 2 (229) 76,881 Total available-for-sale investment securities $ 125,941 $ 2 $ (267) $ 125,676 As of June 30, 2022, the decline in fair value below amortized cost basis was not considered other than temporary as it is more likely than not we will hold the securities until maturity or recovery of the cost basis. No allowance for credit losses for available-for-sale investment securities was recorded as of June 30, 2022 or December 31, 2021. The fair values of available-for-sale investment securities, by remaining contractual maturity, are as follows (in thousands): June 30, 2022 December 31, 2021 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Due in one year or less $ 75,878 $ 75,425 $ 64,627 $ 64,600 Due after one year through three years 51,464 49,909 61,314 61,076 Total available-for-sale investment securities $ 127,342 $ 125,334 $ 125,941 $ 125,676 During the six months ended June 30, 2022 and 2021, we had sales and maturities (which include calls) of investment securities, as follows (in thousands): Six Months Ended June 30, 2022 Gross Realized Gains Gross Realized Losses Gross Proceeds from Sales Gross Proceeds from Maturities Corporate bonds $ — $ — $ — $ 23,998 Treasury securities — — — 19,500 Total $ — $ — $ — $ 43,498 Six Months Ended June 30, 2021 Gross Realized Gains Gross Realized Losses Gross Proceeds from Sales Gross Proceeds from Maturities Agency securities $ — $ — $ — $ 5,250 Treasury securities 6 — 42,198 21,500 Total $ 6 $ — $ 42,198 $ 26,750 Fair Value Measurements Recurring Fair Value Measurements The following tables present our financial assets and liabilities measured at fair value on a recurring basis as of June 30, 2022 and December 31, 2021 by level within the fair value hierarchy (in thousands): June 30, 2022 Level 1 Level 2 Total Fair Cash equivalents: Money market funds $ 4,784 $ — $ 4,784 Available-for-sale investment securities: Corporate bonds — 19,404 19,404 Agency securities — 19,309 19,309 Treasury securities 86,621 — 86,621 Total $ 91,405 $ 38,713 $ 130,118 December 31, 2021 Level 1 Level 2 Total Fair Cash equivalents: Money market funds $ 6,105 $ — $ 6,105 Available-for-sale investment securities: Corporate bonds — 29,069 29,069 Agency securities — 19,726 19,726 Treasury securities 76,881 — 76,881 Total $ 82,986 $ 48,795 $ 131,781 The carrying amounts of cash and cash equivalents, restricted cash, accounts receivable, accounts payable and accrued liabilities approximate their fair value because of the short maturity of these items. Fair value for our Level 1 investment securities is based on market prices for identical assets. Our Level 2 securities were priced by a pricing vendor. The pricing vendor utilizes the most recent observable market information in pricing these securities or, if specific prices are not available for these securities, other observable inputs like market transactions involving comparable securities are used. |