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Business Segments (Segment Expenses Included Within Incurred Claims and Benefits) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2025 | Mar. 31, 2024
Segment Reporting, Revenue Reconciling Item [Line Items] |  |
Non-catastrophe net incurred claim and claim adjustment expenses related to current year | $ 80 | $ 113
(Favorable) unfavorable development | 83 | (7)
Property and Casualty Segments | Specialty |  |
Segment Reporting, Revenue Reconciling Item [Line Items] |  |
Non-catastrophe net incurred claim and claim adjustment expenses related to current year | 499 | 482
Catastrophe losses | 0 | 0
(Favorable) unfavorable development | 10 | (5)
Property and Casualty Segments | Commercial |  |
Segment Reporting, Revenue Reconciling Item [Line Items] |  |
Non-catastrophe net incurred claim and claim adjustment expenses related to current year | 868 | 746
Catastrophe losses | 86 | 82
(Favorable) unfavorable development | 51 | (2)
Property and Casualty Segments | International |  |
Segment Reporting, Revenue Reconciling Item [Line Items] |  |
Non-catastrophe net incurred claim and claim adjustment expenses related to current year | 181 | 183
Catastrophe losses | 11 | 6
(Favorable) unfavorable development | $ 0 | $ 0

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- Definition Amount, after effects of reinsurance, of payments to settle claims incurred in the current period 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 (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-3 + Details
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- Definition The charge against earnings in the period for the uninsured portion of a loss from a fire, explosion, or natural disaster (hurricane, earthquake). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(9)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2 + Details
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