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Unpaid losses and loss expenses Unpaid losses and loss expenses (PPD table) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2022 | Sep. 30, 2021
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | $ (222) | $ (321) | $ (709) | $ (781)
North America Commercial P&C Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | (166) | (157) | (561) | (440)
North America Personal P&C Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | (133) | (182) | (187) | (266)
North American Agriculture Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | 9 | 7 | (17) | 5
Overseas General Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | (5) | (28) | (238) | (209)
Global Reinsurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | 0 | (4) | 22 | (11)
Short Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | (261) | (246) | (654) | (644)
Short Tail [Member] | North America Commercial P&C Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | (137) | (56) | (246) | (197)
Short Tail [Member] | North America Personal P&C Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | (133) | (182) | (187) | (266)
Short Tail [Member] | North American Agriculture Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | 9 | 7 | (17) | 5
Short Tail [Member] | Overseas General Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | 0 | (15) | (233) | (201)
Short Tail [Member] | Global Reinsurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | 0 | 0 | 29 | 15
Short Tail [Member] | Corporate Segment [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | 0 | 0 | 0 | 0
Long Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | 39 | (75) | (55) | (137)
Long Tail [Member] | North America Commercial P&C Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | (29) | (101) | (315) | (243)
Long Tail [Member] | North America Personal P&C Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | 0 | 0 | 0 | 0
Long Tail [Member] | North American Agriculture Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | 0 | 0 | 0 | 0
Long Tail [Member] | Overseas General Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | (5) | (13) | (5) | (8)
Long Tail [Member] | Global Reinsurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | 0 | (4) | (7) | (26)
Long Tail [Member] | Corporate Segment [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net Prior Period Development | $ 73 | $ 43 | $ 272 | $ 140

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