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Investments - Fixed Maturity Securities and Short Term Investments (Details) - USD ($) $ in Millions | Jun. 30, 2022 | Mar. 31, 2022 | Dec. 31, 2021 | Jun. 30, 2021 | Mar. 31, 2021 | Dec. 31, 2020
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Schedule of Investments [Line Items] |  |  |  |  |  |
Percent of Total | 100.00% |  | 100.00% |  |  |
Amortized Cost | $ 7,803 |  | $ 7,822 |  |  |
Allowance for Credit Losses | (51) | $ (47) | (42) | $ (39) | $ (81) | $ (78)
Gross Unrealized Gains | 88 |  | 478 |  |  |
Gross Unrealized Losses | (444) |  | (56) |  |  |
Estimated Fair Value | 7,396 |  | 8,202 |  |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (132) |  | $ (30) |  |  |
Government agency obligations as a percentage of total mortgage backed securities | 31.00% |  | 31.00% |  |  |
Obligations of state and political subdivisions |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Percent of Total | 45.00% |  | 43.00% |  |  |
Amortized Cost | $ 3,542 |  | $ 3,386 |  |  |
Allowance for Credit Losses | (14) |  | (12) |  |  |
Gross Unrealized Gains | 57 |  | 290 |  |  |
Gross Unrealized Losses | (101) |  | (4) |  |  |
Estimated Fair Value | 3,484 |  | 3,660 |  |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (5) |  | $ 0 |  |  |
U.S. government and agencies |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Percent of Total | 2.00% |  | 2.00% |  |  |
Amortized Cost | $ 122 |  | $ 123 |  |  |
Allowance for Credit Losses | 0 |  | 0 |  |  |
Gross Unrealized Gains | 3 |  | 7 |  |  |
Gross Unrealized Losses | (6) |  | (2) |  |  |
Estimated Fair Value | 119 |  | 128 |  |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ 0 |  | $ 0 |  |  |
Corporate securities |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Percent of Total | 31.00% |  | 32.00% |  |  |
Amortized Cost | $ 2,434 |  | $ 2,516 |  |  |
Allowance for Credit Losses | (4) |  | (1) |  |  |
Gross Unrealized Gains | 3 |  | 111 |  |  |
Gross Unrealized Losses | (239) |  | (21) |  |  |
Estimated Fair Value | 2,194 |  | 2,605 |  |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (78) |  | $ (4) |  |  |
RMBS |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Percent of Total | 5.00% |  | 6.00% |  |  |
Amortized Cost | $ 419 |  | $ 454 |  |  |
Allowance for Credit Losses | (15) |  | (17) |  |  |
Gross Unrealized Gains | 5 |  | 24 |  |  |
Gross Unrealized Losses | (40) |  | (24) |  |  |
Estimated Fair Value | 369 |  | 437 |  |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (35) |  | $ (24) |  |  |
CMBS |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Percent of Total | 4.00% |  | 4.00% |  |  |
Amortized Cost | $ 303 |  | $ 332 |  |  |
Allowance for Credit Losses | 0 |  | 0 |  |  |
Gross Unrealized Gains | 0 |  | 14 |  |  |
Gross Unrealized Losses | (5) |  | 0 |  |  |
Estimated Fair Value | 298 |  | 346 |  |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ 0 |  | $ 0 |  |  |
CLOs and CLO warehouse assets: |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Percent of Total | 6.00% |  | 6.00% |  |  |
Amortized Cost | $ 442 |  | $ 457 |  |  |
Allowance for Credit Losses | 0 |  | 0 |  |  |
Gross Unrealized Gains | 0 |  | 1 |  |  |
Gross Unrealized Losses | (21) |  | 0 |  |  |
Estimated Fair Value | 421 |  | 458 |  |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ 0 |  | $ 0 |  |  |
Others |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Percent of Total | 5.00% |  | 5.00% |  |  |
Amortized Cost | $ 419 |  | $ 420 |  |  |
Allowance for Credit Losses | (18) |  | (12) |  |  |
Gross Unrealized Gains | 20 |  | 26 |  |  |
Gross Unrealized Losses | (13) |  | (2) |  |  |
Estimated Fair Value | 408 |  | 432 |  |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (12) |  | $ (2) |  |  |
Non-U.S. government securities |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Percent of Total | 2.00% |  | 2.00% |  |  |
Amortized Cost | $ 122 |  | $ 134 |  |  |
Allowance for Credit Losses | 0 |  | 0 |  |  |
Gross Unrealized Gains | 0 |  | 5 |  |  |
Gross Unrealized Losses | (19) |  | (3) |  |  |
Estimated Fair Value | 103 |  | 136 |  |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (2) |  | $ 0 |  |  |

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