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Investments - Fixed Maturity Securities and Short Term Investments (Details) - USD ($) $ in Millions | Mar. 31, 2022 | Dec. 31, 2021 | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | --- | --- | ---
Schedule of Investments [Line Items] |  |  |  |
Allowance for Credit Losses | $ (47) | $ (42) | $ (81) | $ (78)
Estimated Fair Value | $ 8,156 | $ 8,202 |  |
Government agency obligations as a percentage of total mortgage backed securities | 30.00% | 31.00% |  |
Fixed-maturity securities, available-for-sale |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 100.00% | 100.00% |  |
Amortized Cost | $ 8,227 | $ 7,822 |  |
Allowance for Credit Losses | (47) | (42) |  |
Gross Unrealized Gains | 180 | 478 |  |
Gross Unrealized Losses | (204) | (56) |  |
Estimated Fair Value | 8,156 | 8,202 |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (78) | $ (30) |  |
Fixed-maturity securities, available-for-sale | Obligations of state and political subdivisions |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 47.00% | 43.00% |  |
Amortized Cost | $ 3,893 | $ 3,386 |  |
Allowance for Credit Losses | (13) | (12) |  |
Gross Unrealized Gains | 115 | 290 |  |
Gross Unrealized Losses | (54) | (4) |  |
Estimated Fair Value | 3,941 | 3,660 |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (3) | $ 0 |  |
Fixed-maturity securities, available-for-sale | 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 | 5 | 7 |  |
Gross Unrealized Losses | (5) | (2) |  |
Estimated Fair Value | 122 | 128 |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ 0 | $ 0 |  |
Fixed-maturity securities, available-for-sale | Corporate securities |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 30.00% | 32.00% |  |
Amortized Cost | $ 2,469 | $ 2,516 |  |
Allowance for Credit Losses | (5) | (1) |  |
Gross Unrealized Gains | 26 | 111 |  |
Gross Unrealized Losses | (102) | (21) |  |
Estimated Fair Value | 2,388 | 2,605 |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (44) | $ (4) |  |
Fixed-maturity securities, available-for-sale | RMBS |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 5.00% | 6.00% |  |
Amortized Cost | $ 437 | $ 454 |  |
Allowance for Credit Losses | (18) | (17) |  |
Gross Unrealized Gains | 10 | 24 |  |
Gross Unrealized Losses | (29) | (24) |  |
Estimated Fair Value | 400 | 437 |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (28) | $ (24) |  |
Fixed-maturity securities, available-for-sale | CMBS |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 4.00% | 4.00% |  |
Amortized Cost | $ 321 | $ 332 |  |
Allowance for Credit Losses | 0 | 0 |  |
Gross Unrealized Gains | 2 | 14 |  |
Gross Unrealized Losses | (1) | 0 |  |
Estimated Fair Value | 322 | 346 |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ 0 | $ 0 |  |
Fixed-maturity securities, available-for-sale | CLOs and CLO warehouse assets: |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 5.00% | 6.00% |  |
Amortized Cost | $ 440 | $ 457 |  |
Allowance for Credit Losses | 0 | 0 |  |
Gross Unrealized Gains | 0 | 1 |  |
Gross Unrealized Losses | (3) | 0 |  |
Estimated Fair Value | 437 | 458 |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ 0 | $ 0 |  |
Fixed-maturity securities, available-for-sale | Others |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 5.00% | 5.00% |  |
Amortized Cost | $ 422 | $ 420 |  |
Allowance for Credit Losses | (11) | (12) |  |
Gross Unrealized Gains | 22 | 26 |  |
Gross Unrealized Losses | (3) | (2) |  |
Estimated Fair Value | 430 | 432 |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (2) | $ (2) |  |
Fixed-maturity securities, available-for-sale | Non-U.S. government securities |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Percent of Total | 2.00% | 2.00% |  |
Amortized Cost | $ 123 | $ 134 |  |
Allowance for Credit Losses | 0 | 0 |  |
Gross Unrealized Gains | 0 | 5 |  |
Gross Unrealized Losses | (7) | (3) |  |
Estimated Fair Value | 116 | 136 |  |
AOCI Pre-tax Gain (Loss) on Securities with Credit Loss | $ (1) | $ 0 |  |

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