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Reserve for Losses and Loss Adjustment Expenses - Prior year development (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | $ (121) | $ (146) | $ (366) | $ (403)
Operating segments |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (121) | (146) | (366) | (403)
Operating segments | Short tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (163) | (186) | (439) | (485)
Operating segments | Long tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | 42 | 40 | 73 | 82
Operating segments | Insurance |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (16) | (10) | (31) | (34)
Operating segments | Insurance | Short tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (31) | (29) | (61) | (74)
Operating segments | Insurance | Short tailed lines | Property And Marine Product Line |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (15) | (16) |  | (44)
Operating segments | Insurance | Short tailed lines | Travel and accident |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (11) |  | (29) |
Operating segments | Insurance | Short tailed lines | Warranty and lenders solutions |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse |  |  |  | (20)
Operating segments | Insurance | Short tailed lines | Surety Product Line |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse |  |  | (31) |
Operating segments | Insurance | Long tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | 15 | 19 | 30 | 40
Operating segments | Insurance | Long tailed lines | Professional liability |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse |  | 25 |  | 48
Operating segments | Insurance | Long tailed lines | Executive assurance |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse |  |  |  | (24)
Operating segments | Reinsurance |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (41) | (44) | (115) | (126)
Operating segments | Reinsurance | Short tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (68) | (65) | (158) | (168)
Operating segments | Reinsurance | Short tailed lines | Property other than property catastrophe |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (20) | (29) | (71) | (75)
Operating segments | Reinsurance | Short tailed lines | Property catastrophe |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse |  | (22) |  | (29)
Operating segments | Reinsurance | Short tailed lines | Other specialty lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (35) | (19) | (72) | (46)
Operating segments | Reinsurance | Long tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | 27 | 21 | 43 | 42
Operating segments | Reinsurance | Long tailed lines | Casualty |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | 27 | 21 | 43 | 39
Operating segments | Mortgage |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (64) | (92) | (220) | (243)
Operating segments | Mortgage | Short tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | (64) | (92) | (220) | (243)
Operating segments | Mortgage | Long tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development (favorable) adverse | $ 0 | $ 0 | $ 0 | $ 0

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- Definition Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480046/944-40-55-7 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-3 + Details
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