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Reserve for Losses and Loss Adjustment Expenses - Prior year development (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2023 | Mar. 31, 2022
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Prior year development favorable (unfavorable) | $ 136 | $ 141
Operating segments | Insurance |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Prior year development favorable (unfavorable) | $ 12 | $ 7
Percentage of prior year development | 0.90% | 0.70%
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) | $ (13) |
Operating segments | Insurance | Medium tailed lines | Programs |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Prior year development favorable (unfavorable) |  | $ 5
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) | (18) | (7)
Operating segments | Insurance | Medium tailed lines | Contract binding |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Prior year development favorable (unfavorable) |  | (6)
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) | 7 |
Operating segments | Insurance | Long tailed lines | Casualty |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Prior year development favorable (unfavorable) |  | (6)
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) | 1 |
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) |  | 19
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) | 9 |
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 |
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 | 19
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) |  | (12)
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) | 25 |
Operating segments | Reinsurance |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Prior year development favorable (unfavorable) | $ 53 | $ 32
Percentage of prior year development | 4.00% | 4.00%
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) | $ 2 | $ 11
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) |  | (3)
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) | 3 |
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) |  | 35
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) | 49 |
Operating segments | Reinsurance | Short tailed lines | Property catastrophe and 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) |  | 19
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) | 8 |
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) | 23 |
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) | 18 |
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) | 3 |
Operating segments | Mortgage |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Prior year development favorable (unfavorable) | $ 71 | $ 102
Percentage of prior year development | 23.90% | 35.30%

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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/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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