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INVESTMENT SECURITIES
 3 Months Ended
Mar. 31, 2024
Investments, Debt and Equity Securities [Abstract]  
INVESTMENT SECURITIES INVESTMENT SECURITIES
Investment securities classified as current and long-term were as follows at March 31, 2024 and December 31, 2023, respectively:
Amortized
Cost		Gross
Unrealized
Gains		Gross
Unrealized
Losses		Fair
Value
 (in millions)
March 31, 2024
U.S. Treasury and other U.S. government
    corporations and agencies:
U.S. Treasury and agency obligations$2,928 $— $(84)$2,844 
Mortgage-backed securities3,925 — (486)3,439 
Tax-exempt municipal securities850 — (24)826 
Mortgage-backed securities:
Residential462 — (68)394 
Commercial1,420 1 (113)1,308 
Asset-backed securities1,552 2 (37)1,517 
Corporate debt securities7,348 24 (623)6,749 
Total debt securities$18,485 $27 $(1,435)17,077 
December 31, 2023
U.S. Treasury and other U.S. government
    corporations and agencies:
U.S. Treasury and agency obligations$2,717 $1 $(51)$2,667 
Mortgage-backed securities3,946 1 (425)3,522 
Tax-exempt municipal securities879 1 (22)858 
Mortgage-backed securities:
Residential465 1 (66)400 
Commercial1,471 — (126)1,345 
Asset-backed securities1,813 2 (44)1,771 
Corporate debt securities7,011 28 (594)6,445 
Total debt securities$18,302 $34 $(1,328)17,008 
We own certain corporate debt securities of Gentiva Hospice. The book value and fair value are $379 million and $397 million, respectively, at March 31, 2024. The book value and fair value were $379 million and $398 million, respectively, at December 31, 2023.
Gross unrealized losses and fair values aggregated by investment category and length of time of individual debt securities that have been in a continuous unrealized loss position for which no allowances for credit loss has been recorded were as follows at March 31, 2024 and December 31, 2023, respectively:
 Less than 12 months12 months or moreTotal
 Fair
Value		Gross
Unrealized
Losses		Fair
Value		Gross
Unrealized
Losses		Fair
Value		Gross
Unrealized
Losses
 (in millions)
March 31, 2024
U.S. Treasury and other U.S. government corporations and agencies:
U.S. Treasury and agency obligations$2,301 $(43)$447 $(41)$2,748 $(84)
Mortgage-backed securities862 (15)2,513 (471)3,375 (486)
Tax-exempt municipal securities261 (1)508 (23)769 (24)
Mortgage-backed securities:
Residential9 — 365 (68)374 (68)
Commercial— — 1,242 (113)1,242 (113)
Asset-backed securities447 (2)787 (35)1,234 (37)
Corporate debt securities824 (7)4,702 (616)5,526 (623)
Total debt securities$4,704 $(68)$10,564 $(1,367)$15,268 $(1,435)
December 31, 2023
U.S. Treasury and other U.S. government corporations and agencies:
U.S. Treasury and agency obligations$1,899 $(12)$431 $(39)$2,330 $(51)
Mortgage-backed securities958 (12)2,269 (413)3,227 (425)
Tax-exempt municipal securities160 (1)523 (21)683 (22)
Mortgage-backed securities:
Residential— — 373 (66)373 (66)
Commercial18 — 1,303 (126)1,321 (126)
Asset-backed securities120 (1)1,364 (43)1,484 (44)
Corporate debt securities466 (2)4,783 (592)5,249 (594)
Total debt securities$3,621 $(28)$11,046 $(1,300)$14,667 $(1,328)

Approximately 97% of our debt securities were investment-grade quality, with a weighted average credit rating of AA- by Standard & Poor's Rating Service, or S&P, at March 31, 2024. Our remaining debt securities below investment-grade were primarily rated B+, the higher end of the below investment-grade rating scale. Tax-exempt municipal securities were diversified among general obligation bonds of states and local municipalities in the United States as well as special revenue bonds issued by municipalities to finance specific public works projects such as utilities, water and sewer, transportation, or education. Our general obligation bonds are diversified across the United States with no individual state exceeding approximately 1% of our total debt securities. Our investment policy limits investments in a single issuer and requires diversification among various asset types.
Our unrealized losses from all debt securities were generated from approximately 1,685 positions out of a total of approximately 2,100 positions at March 31, 2024. All issuers of debt securities we own that were trading at an
unrealized loss at March 31, 2024 remain current on all contractual payments. After taking into account these and other factors previously described, we believe these unrealized losses primarily were caused by an increase in market interest rates in the current markets since the time these debt securities were purchased. At March 31, 2024, we did not intend to sell any debt securities with an unrealized loss position in accumulated other comprehensive income, and it is not likely that we will be required to sell these debt securities before recovery of their amortized cost basis. Additionally, we did not record any material credit allowances for debt securities that were in an unrealized loss position for the three months ended March 31, 2024 or 2023.
The detail of gains (losses) related to investment securities and included within investment income was as follows for the three months ended March 31, 2024 and 2023:
 Three Months Ended March 31,
 20242023
 (in millions)
Gross gains on investment securities$2 $— 
Gross losses on investment securities(1)(61)
Gross gains on equity securities— 1 
Gross losses on equity securities— — 
Net recognized gains (losses) on investment securities$1 $(60)
The gains and losses related to equity securities for the three months ended March 31, 2024 and 2023 was as follows:
Three Months Ended March 31,
20242023
(in millions)
Net gains (losses) recognized on equity securities during the period$— $1 
Less: Net gains (losses) recognized on equity securities sold during the period— 1 
Unrealized gains (losses) recognized on equity securities still held at the end of the period$— $— 
The contractual maturities of debt securities available for sale at March 31, 2024, regardless of their balance sheet classification, are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.
Amortized
Cost		Fair
Value
 (in millions)
Due within one year$1,235 $1,229 
Due after one year through five years5,402 5,199 
Due after five years through ten years3,259 2,954 
Due after ten years1,230 1,037 
Mortgage and asset-backed securities7,359 6,658 
Total debt securities$18,485 $17,077 
For additional information regarding our investment securities, refer to Note 2 to the audited Consolidated Financial Statements included in Part II, Item 8, "Financial Statements and Supplementary Data" in our 2023 Form 10-K.