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Claim and Claim Adjustment Expense Reserves and Future Policy Benefit Reserves (Gross and Net Carried Claim and Claim Adjustment Expense Reserves) (Details) - USD ($) $ in Millions | Dec. 31, 2022 | Sep. 30, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | --- | --- | --- | ---
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
Gross Case Reserves | $ 10,387 |  | $ 10,555 |  |
Gross IBNR Reserves | 14,712 | $ 107 | 13,619 |  |
Total Gross Carried Claim and Claim Adjustment Expense Reserves | 25,099 |  | 24,174 | $ 22,706 | $ 21,720
Net Case Reserves | 8,319 |  | 8,369 |  |
Net IBNR Reserves | 11,589 |  | 10,836 |  |
Total Net Carried Claim and Claim Adjustment Expense Reserves | 19,908 |  | 19,205 | $ 18,701 | $ 17,885
Specialty |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
Gross Case Reserves | 1,529 |  | 1,578 |  |
Gross IBNR Reserves | 5,349 |  | 4,855 |  |
Total Gross Carried Claim and Claim Adjustment Expense Reserves | 6,878 |  | 6,433 |  |
Net Case Reserves | 1,310 |  | 1,338 |  |
Net IBNR Reserves | 4,253 |  | 3,927 |  |
Total Net Carried Claim and Claim Adjustment Expense Reserves | 5,563 |  | 5,265 |  |
Commercial |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
Gross Case Reserves | 3,156 |  | 3,184 |  |
Gross IBNR Reserves | 6,239 |  | 5,706 |  |
Total Gross Carried Claim and Claim Adjustment Expense Reserves | 9,395 |  | 8,890 |  |
Net Case Reserves | 2,809 |  | 2,850 |  |
Net IBNR Reserves | 5,621 |  | 5,215 |  |
Total Net Carried Claim and Claim Adjustment Expense Reserves | 8,430 |  | 8,065 |  |
International |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
Gross Case Reserves | 817 |  | 859 |  |
Gross IBNR Reserves | 1,586 |  | 1,421 |  |
Total Gross Carried Claim and Claim Adjustment Expense Reserves | 2,403 |  | 2,280 |  |
Net Case Reserves | 686 |  | 744 |  |
Net IBNR Reserves | 1,317 |  | 1,196 |  |
Total Net Carried Claim and Claim Adjustment Expense Reserves | 2,003 |  | 1,940 |  |
Life & Group |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
Gross Case Reserves | 3,457 |  | 3,383 |  |
Gross IBNR Reserves | 217 |  | 371 |  |
Total Gross Carried Claim and Claim Adjustment Expense Reserves | 3,674 |  | 3,754 |  |
Net Case Reserves | 3,377 |  | 3,291 |  |
Net IBNR Reserves | 196 |  | 350 |  |
Total Net Carried Claim and Claim Adjustment Expense Reserves | 3,573 |  | 3,641 |  |
Corporate & Other |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
Gross Case Reserves | 1,428 |  | 1,551 |  |
Gross IBNR Reserves | 1,321 |  | 1,266 |  |
Total Gross Carried Claim and Claim Adjustment Expense Reserves | 2,749 |  | 2,817 |  |
Net Case Reserves | 137 |  | 146 |  |
Net IBNR Reserves | 202 |  | 148 |  |
Total Net Carried Claim and Claim Adjustment Expense Reserves | $ 339 |  | $ 294 |  |

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