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Reserve for Losses and Loss Adjustment Expenses - Prior year development (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 121 | $ 121 | $ 245 | $ 257
Operating segments |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | 121 | 121 | 245 | 257
Operating segments | Insurance |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 5 | $ 12 | $ 15 | $ 24
Percentage of prior year development | 0.30% | 0.90% | 0.50% | 0.90%
Operating segments | Insurance | Medium tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | $ (18) |  | $ (31)
Operating segments | Insurance | Medium tailed lines | Professional liability |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | (5) |  | (24)
Operating segments | Insurance | Medium tailed lines | Marine |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | (4) | $ (69) |
Operating segments | Insurance | Medium tailed lines | Programs Business |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | (8) | (17) | (6)
Operating segments | Insurance | Medium tailed lines | Surety Product Line |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  |  | 25 |
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 (unfavorable) |  | 6 |  | 16
Operating segments | Insurance | Long tailed lines | Alternative markets |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  |  |  | 5
Operating segments | Insurance | Long tailed lines | Healthcare Business |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  |  |  | (5)
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 (unfavorable) | $ 45 |  | 74 |
Operating segments | Insurance | Short tailed lines | Property excluding marine |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | 36 | 16 | 54 | 25
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 (unfavorable) |  | 7 |  | 14
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 (unfavorable) | 8 |  | 18 |
Operating segments | Insurance | Medium tailed and long tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | (40) |  | (59) |
Operating segments | Insurance | Medium tailed and long tailed lines | Marine |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | (52) |  |  |
Operating segments | Insurance | Medium tailed and long tailed lines | Programs Business |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | (9) |  |  |
Operating segments | Insurance | Medium tailed and long tailed lines | Surety Product Line |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | 20 |  |  |
Operating segments | Insurance | Short tailed and long tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | 30 |  | 55
Operating segments | Reinsurance |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 34 | $ 29 | $ 74 | $ 82
Percentage of prior year development | 1.90% | 2.20% | 2.20% | 3.00%
Operating segments | Reinsurance | Medium tailed lines | Marine and aviation |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | $ 7 | $ (5) | $ 9
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 (unfavorable) |  | (22) |  | (21)
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 (unfavorable) |  | (22) | (17) | (19)
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 (unfavorable) | $ 51 |  | 95 |
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 (unfavorable) | 18 |  | 10 | 7
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 (unfavorable) | 30 | 23 | 51 | 46
Operating segments | Reinsurance | Short tailed lines | Other specialty lines and other lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | 21 |  |
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 (unfavorable) |  |  | 37 | 27
Operating segments | Reinsurance | Short tailed lines | Other lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  |  |  | 13
Operating segments | Reinsurance | Medium tailed and long tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | (17) |  | (21) |
Operating segments | Reinsurance | Medium tailed and long tailed lines | Casualty |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | (14) |  |  |
Operating segments | Reinsurance | Short tailed and medium tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | 51 |  | 103
Operating segments | Mortgage |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 82 | $ 80 | $ 156 | $ 151
Percentage of prior year development | 26.90% | 27.20% | 25.60% | 25.60%

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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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