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Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions | Mar. 31, 2022 | Dec. 31, 2021 | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | --- | --- | ---
Fixed maturity securities available-for-sale: |  |  |  |
Gross Unrealized Gains | $ 2,191 | $ 4,558 |  |
Gross Unrealized Losses | 1,157 | 112 |  |
Allowance for Credit Losses | 17 | 18 | $ 43 | $ 40
Estimated Fair Value | 41,939 | 44,373 |  |
Total fixed maturity securities trading |  |  |  |
Debt securities, amortized cost | 40,928 | 39,952 |  |
Total fixed maturity securities | 41,945 | 44,380 |  |
Corporate and other bonds |  |  |  |
Fixed maturity securities available-for-sale: |  |  |  |
Cost or Amortized Cost | 22,001 | 21,444 |  |
Gross Unrealized Gains | 1,277 | 2,755 |  |
Gross Unrealized Losses | 486 | 56 |  |
Allowance for Credit Losses | 12 | 11 | 27 | 23
Estimated Fair Value | 22,780 | 24,132 |  |
Total fixed maturity securities trading |  |  |  |
Total fixed maturity securities | 23,475 | 24,852 |  |
States, municipalities and political subdivisions |  |  |  |
Fixed maturity securities available-for-sale: |  |  |  |
Cost or Amortized Cost | 10,516 | 10,358 |  |
Gross Unrealized Gains | 862 | 1,599 |  |
Gross Unrealized Losses | 319 | 14 |  |
Allowance for Credit Losses | 0 | 0 |  |
Estimated Fair Value | 11,059 | 11,943 |  |
Total fixed maturity securities trading |  |  |  |
Total fixed maturity securities | 11,059 | 11,943 |  |
Asset-backed |  |  |  |
Fixed maturity securities available-for-sale: |  |  |  |
Cost or Amortized Cost | 7,701 | 7,441 |  |
Gross Unrealized Gains | 49 | 188 |  |
Gross Unrealized Losses | 334 | 37 |  |
Allowance for Credit Losses | 5 | 7 | $ 16 | $ 17
Estimated Fair Value | 7,411 | 7,585 |  |
Total fixed maturity securities trading |  |  |  |
Total fixed maturity securities | 7,411 | 7,585 |  |
Residential mortgage-backed |  |  |  |
Fixed maturity securities available-for-sale: |  |  |  |
Cost or Amortized Cost | 2,983 | 2,893 |  |
Gross Unrealized Gains | 25 | 71 |  |
Gross Unrealized Losses | 160 | 8 |  |
Allowance for Credit Losses | 0 | 0 |  |
Estimated Fair Value | 2,848 | 2,956 |  |
Commercial mortgage-backed |  |  |  |
Fixed maturity securities available-for-sale: |  |  |  |
Cost or Amortized Cost | 2,008 | 1,987 |  |
Gross Unrealized Gains | 13 | 63 |  |
Gross Unrealized Losses | 81 | 19 |  |
Allowance for Credit Losses | 0 | 0 |  |
Estimated Fair Value | 1,940 | 2,031 |  |
Other asset-backed |  |  |  |
Fixed maturity securities available-for-sale: |  |  |  |
Cost or Amortized Cost | 2,710 | 2,561 |  |
Gross Unrealized Gains | 11 | 54 |  |
Gross Unrealized Losses | 93 | 10 |  |
Allowance for Credit Losses | 5 | 7 |  |
Estimated Fair Value | 2,623 | 2,598 |  |
Fixed maturity securities |  |  |  |
Fixed maturity securities available-for-sale: |  |  |  |
Cost or Amortized Cost | 40,922 | 39,945 |  |
Gross Unrealized Gains | 2,191 | 4,558 |  |
Gross Unrealized Losses | 1,157 | 112 |  |
Allowance for Credit Losses | 17 | 18 |  |
Estimated Fair Value | 41,939 | 44,373 |  |
U.S. Treasury and obligations of government-sponsored enterprises |  |  |  |
Fixed maturity securities available-for-sale: |  |  |  |
Cost or Amortized Cost | 125 | 132 |  |
Gross Unrealized Gains | 0 | 1 |  |
Gross Unrealized Losses | 5 | 3 |  |
Allowance for Credit Losses | 0 | 0 |  |
Estimated Fair Value | 120 | 130 |  |
Foreign government |  |  |  |
Fixed maturity securities available-for-sale: |  |  |  |
Cost or Amortized Cost | 559 | 570 |  |
Gross Unrealized Gains | 3 | 15 |  |
Gross Unrealized Losses | 13 | 2 |  |
Allowance for Credit Losses | 0 | 0 |  |
Estimated Fair Value | 549 | 583 |  |
Redeemable preferred stock |  |  |  |
Fixed maturity securities available-for-sale: |  |  |  |
Cost or Amortized Cost | 20 | 0 |  |
Gross Unrealized Gains | 0 | 0 |  |
Gross Unrealized Losses | 0 | 0 |  |
Allowance for Credit Losses | 0 | 0 |  |
Estimated Fair Value | 20 | 0 |  |
Total fixed maturity securities trading |  |  |  |
Total fixed maturity securities trading |  |  |  |
Cost or amortized cost, trading securities | 6 | 7 |  |
Estimated fair value, trading securities | $ 6 | $ 7 |  |

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