INVESTMENTS | INVESTMENTS The following tables provide summaries of the Company's investments by major security type as of March 31, 2023 and December 31, 2022: March 31, 2023 Amortized Cost Unrealized Gains Unrealized Losses Fair Value (in thousands) U.S. treasury and agency securities $ 1,051,796 $ 403 $ (2,301) $ 1,049,898 Corporate notes 339,893 226 (2,506) 337,613 Certificate of deposit 53,194 — — 53,194 Commercial paper 32,101 — — 32,101 Municipalities 17,220 — (243) 16,977 Total $ 1,494,204 $ 629 $ (5,050) $ 1,489,783 December 31, 2022 Amortized Cost Unrealized Gains Unrealized Losses Fair Value (in thousands) U.S. treasury and agency securities $ 1,160,430 $ 89 $ (5,237) $ 1,155,282 Corporate notes 378,481 66 (4,098) 374,449 Certificate of deposit 38,082 — — 38,082 Commercial paper 32,730 — — 32,730 Municipalities 20,091 — (428) 19,663 Total $ 1,629,814 $ 155 $ (9,763) $ 1,620,206 The following table summarizes those available-for-sale investments that have been in a continuous loss position for less than 12 months at March 31, 2023 and December 31, 2022. March 31, 2023 Number of Securities Fair Value Gross (in thousands), except no. of securities U.S. treasury and agency securities 167 $ 531,375 $ (204) Corporate notes 130 163,507 (579) Municipalities 5 $ 3,061 (61) Total 302 $ 697,943 $ (844) December 31, 2022 Number of Securities Fair Value Gross (in thousands), except no. of securities U.S. treasury and agency securities 165 $ 586,411 $ (973) Corporate notes 138 135,133 (731) Municipalities 5 3,070 (71) Total 308 $ 724,614 $ (1,775) The following table summarizes those available-for-sale securities that have been in a continuous unrealized loss position for longer than twelve months as of March 31, 2023 and December 31, 2022. March 31, 2023 Number of Securities Fair Value Gross (in thousands), except no. of securities U.S. treasury and agency securities 23 $ 100,671 $ (2,096) Corporate notes 130 126,524 (1,928) Municipalities 36 $ 13,916 (182) Total 189 $ 241,111 $ (4,206) December 31, 2022 Number of Securities Fair Value Gross (in thousands), except no. of securities U.S. treasury and agency securities 45 $ 298,746 $ (4,264) Corporate notes 189 200,745 (3,367) Municipalities 57 $ 16,594 (357) Total 291 $ 516,085 $ (7,988) The Company monitors available-for-sale debt securities for credit losses and recognizes an allowance for credit losses when factors indicate a decline in the fair value of a security is credit-related. Certain investments may experience a decline in fair value due to changes in market interest rates, changes in general economic conditions, or a deterioration in the credit worthiness of a security's issuer. The Company has assessed the gross unrealized losses during the period and determined an allowance for credit losses is not necessary because the declines in fair value are believed to be due to market fluctuations and not due to credit-related events. The amortized cost and fair value of the Company's fixed maturity securities as of March 31, 2023 by contractual maturity are shown below. Actual maturities of these securities could differ from their contractual maturities because issuers may have the right to call or prepay obligations, with or without penalties. March 31, 2023 Amortized Cost Fair Value (in thousands) Due in one year or less $ 1,329,323 $ 1,324,544 Due after one year through five years 164,881 165,239 Total $ 1,494,204 $ 1,489,783 Net investment income was attributable to the following: March 31, 2023 2022 (in thousands) Interest income $ 28,775 $ 697 Investment discount amortization net of premium accretion 7,324 (1,919) Net realized gain (loss) (43) (581) Total $ 36,056 $ (1,803) The accrued investment income balances presented below are included within other current assets in the consolidated balance sheets. March 31, 2023 December 31, 2022 (in thousands) Accrued investment income $ 6,912 $ 5,074 |