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Undiscounted and Discounted Future Benefit Payments and Gross Premiums (Details) - Life policy reserves: - USD ($) $ in Millions | Sep. 30, 2025 | Jun. 30, 2025 | Dec. 31, 2024 | Sep. 30, 2024 | Jun. 30, 2024 | Dec. 31, 2023
--- | --- | --- | --- | --- | --- | ---
Term Life Insurance |  |  |  |  |  |
Liability for Future Policy Benefit, Activity [Line Items] |  |  |  |  |  |
Undiscounted expected future benefit payments | $ 4,996 |  |  | $ 4,840 |  |
Undiscounted expected future gross premiums | 4,675 |  |  | 4,524 |  |
Discounted expected future benefit payments | 2,792 | $ 2,720 | $ 2,668 | 2,794 | $ 2,634 | $ 2,751
Discounted expected future gross premiums | 2,764 |  |  | 2,736 |  |
Whole Life Insurance |  |  |  |  |  |
Liability for Future Policy Benefit, Activity [Line Items] |  |  |  |  |  |
Undiscounted expected future benefit payments | 1,729 |  |  | 1,702 |  |
Undiscounted expected future gross premiums | 698 |  |  | 687 |  |
Discounted expected future benefit payments | 654 | $ 634 | $ 623 | 668 | $ 619 | $ 657
Discounted expected future gross premiums | $ 427 |  |  | $ 428 |  |

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