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Investments - Fixed Maturity Securities and Short Term Investments (Details) - USD ($) $ in Millions | Mar. 31, 2023 | Dec. 31, 2022 | Mar. 31, 2022 | Dec. 31, 2021
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Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 100.00% | 100.00% |  |
Amortized Cost | $ 7,359 | $ 7,707 |  |
Allowance for Credit Losses | (69) | (65) | $ (47) | $ (42)
Gross Unrealized Gains | 75 | 65 |  |
Gross Unrealized Losses | (496) | (588) |  |
Estimated Fair Value | $ 6,869 | $ 7,119 |  |
Government agency obligations as a percentage of total mortgage backed securities | 32.00% | 30.00% |  |
Obligations of state and political subdivisions |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 43.00% | 45.00% |  |
Amortized Cost | $ 3,161 | $ 3,509 |  |
Allowance for Credit Losses | (14) | (14) |  |
Gross Unrealized Gains | 46 | 37 |  |
Gross Unrealized Losses | (96) | (138) |  |
Estimated Fair Value | $ 3,097 | $ 3,394 |  |
U.S. government and agencies |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 1.00% | 2.00% |  |
Amortized Cost | $ 94 | $ 118 |  |
Allowance for Credit Losses | 0 | 0 |  |
Gross Unrealized Gains | 1 | 1 |  |
Gross Unrealized Losses | (7) | (8) |  |
Estimated Fair Value | $ 88 | $ 111 |  |
Corporate securities |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 33.00% | 31.00% |  |
Amortized Cost | $ 2,408 | $ 2,387 |  |
Allowance for Credit Losses | (6) | (6) |  |
Gross Unrealized Gains | 5 | 2 |  |
Gross Unrealized Losses | (254) | (299) |  |
Estimated Fair Value | $ 2,153 | $ 2,084 |  |
RMBS |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 6.00% | 5.00% |  |
Amortized Cost | $ 429 | $ 418 |  |
Allowance for Credit Losses | (20) | (19) |  |
Gross Unrealized Gains | 3 | 3 |  |
Gross Unrealized Losses | (62) | (62) |  |
Estimated Fair Value | $ 350 | $ 340 |  |
CMBS |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 3.00% | 4.00% |  |
Amortized Cost | $ 267 | $ 282 |  |
Allowance for Credit Losses | 0 | 0 |  |
Gross Unrealized Gains | 0 | 0 |  |
Gross Unrealized Losses | (9) | (11) |  |
Estimated Fair Value | $ 258 | $ 271 |  |
CLOs and CLO warehouse assets: |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 6.00% | 6.00% |  |
Amortized Cost | $ 453 | $ 449 |  |
Allowance for Credit Losses | 0 | 0 |  |
Gross Unrealized Gains | 0 | 0 |  |
Gross Unrealized Losses | (20) | (21) |  |
Estimated Fair Value | $ 433 | $ 428 |  |
Others |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 6.00% | 5.00% |  |
Amortized Cost | $ 426 | $ 423 |  |
Allowance for Credit Losses | (29) | (26) |  |
Gross Unrealized Gains | 20 | 22 |  |
Gross Unrealized Losses | (28) | (26) |  |
Estimated Fair Value | $ 389 | $ 393 |  |
Non-U.S. government securities |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 2.00% | 2.00% |  |
Amortized Cost | $ 121 | $ 121 |  |
Allowance for Credit Losses | 0 | 0 |  |
Gross Unrealized Gains | 0 | 0 |  |
Gross Unrealized Losses | (20) | (23) |  |
Estimated Fair Value | $ 101 | $ 98 |  |

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