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Investments - Additional Information (Details) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2024 USD ($) security | Jun. 30, 2023 USD ($) | Jun. 30, 2024 USD ($) security manager fund | Jun. 30, 2023 USD ($) | Dec. 31, 2023 USD ($) security
Schedule of Investments [Line Items] |  |  |  |  |
Number of outside managers managing investment portfolio | manager |  |  | 3 |  |
Funds accounted for as CIVs | fund |  |  | 3 |  |
Accrued investment income | $ 66 |  | $ 66 |  | $ 71
Number of securities with unrealized losses greater than 10% of book value for 12 months or more | security | 478 |  | 478 |  | 409
Total unrealized losses for securities having losses greater than 10% of book value for 12 months or more | $ 234 |  | $ 234 |  | $ 200
Assets held-in-trust | 74 |  | 74 |  | 234
Sales | 129 | $ 239 | 488 | $ 694 |
Securities purchased with credit deterioration | 0 | $ 0 | 0 | $ 0 |
AGL Subsidiaries |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |
Assets held-in-trust | 1,152 |  | 1,152 |  | $ 1,154
Future Equity Investments |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |
Investments, authorized amount to invest | 1,500 |  | 1,500 |  |
Unfunded commitment | 734 |  | 734 |  |
Investments, fair value disclosure | 810 |  | 810 |  |
Future Equity Investments | Sound Point Capital Management, LP |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |
Investments, authorized amount to invest | $ 1,000 |  | $ 1,000 |  |

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