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Unpaid losses and loss expenses Unpaid losses and loss expenses (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2022 | Dec. 31, 2021
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | $ (200) | $ (247) | $ (396) | $ (487) |  |
Unpaid losses and loss expenses | 76,480 | 73,448 | 76,480 | 73,448 | $ 75,747 | $ 72,330
Net loss and loss expenses paid, Prior Years |  |  | 7,527 | 6,566 |  |
Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease), Gross |  |  | 733 |  |  |
Long Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (72) | (82) | (53) | (94) |  |
Short Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (128) | (165) | (343) | (393) |  |
North America Commercial P&C Insurance [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (146) | (287) | (218) | (395) |  |
North America Commercial P&C Insurance [Member] | Long Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (139) | (266) | (130) | (286) |  |
North America Commercial P&C Insurance [Member] | Short Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (7) | (21) | (88) | (109) |  |
North America Commercial P&C Insurance [Member] | Accident and Health Insurance Product Line [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development |  |  |  | (78) |  |
North America Commercial P&C Insurance [Member] | Workers' Compensation Insurance [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (264) | (286) | (308) | (328) |  |
North America Agricultural Insurance [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (3) | 0 | (3) | (26) |  |
North America Agricultural Insurance [Member] | Long Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | 0 | 0 | 0 | 0 |  |
North America Agricultural Insurance [Member] | Short Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (3) | 0 | (3) | (26) |  |
Corporate Segment [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development |  |  | 70 | 199 |  |
Corporate Segment [Member] | Long Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | 60 | 191 | 70 | 199 |  |
Corporate Segment [Member] | Short Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | 0 | 0 | 0 | 0 |  |
Corporate Segment [Member] | Other [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | 60 |  | 70 |  |  |
Corporate Segment [Member] | Other [Member] | Long Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development |  |  |  | 155 |  |
Overseas General Insurance [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (61) | (173) | (204) | (233) |  |
Overseas General Insurance [Member] | Long Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | 0 | 0 | 0 | 0 |  |
Overseas General Insurance [Member] | Short Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (61) | (173) | (204) | (233) |  |
Overseas General Insurance [Member] | Accident and Health Insurance Product Line [Member] | Short Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development |  | 173 |  | 233 |  |
Overseas General Insurance [Member] | Property, Liability and Casualty Insurance Product Line |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | 61 |  |  |  |  |
Overseas General Insurance [Member] | Property, Liability and Casualty Insurance Product Line | Catastrophe [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development |  |  | 110 |  |  |
North America Personal P&C Insurance [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (33) | (3) | (16) | (54) |  |
North America Personal P&C Insurance [Member] | Long Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | 0 | 0 | 0 | 0 |  |
North America Personal P&C Insurance [Member] | Short Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (33) | (3) | (16) | (54) |  |
Global Reinsurance [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | (17) | 25 | (25) | 22 |  |
Global Reinsurance [Member] | Long Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | 7 | (7) | 7 | (7) |  |
Global Reinsurance [Member] | Short Tail [Member] |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |
Net Prior Period Development | $ (24) | $ 32 | $ (32) | $ 29 |  |

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