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Segments of Operations - Components of underwriting profit, including significant segment expenses by segment and sub-segment (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Segment Reporting Information [Line Items] |  |  |  |
Net earned premiums | $ 2,013 | $ 2,055 | $ 5,240 | $ 5,186
Losses and loss adjustment expenses | 1,355 | 1,430 | 3,327 | 3,279
Commissions and other underwriting expenses | 529 | 518 | 1,593 | 1,527
Operating segments | Property and Casualty Insurance |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Net earned premiums | 2,013 | 2,055 | 5,240 | 5,186
Losses and loss adjustment expenses | 1,355 | 1,430 | 3,327 | 3,274
Commissions and other underwriting expenses | 520 | 510 | 1,568 | 1,494
Property and casualty insurance underwriting profit | 138 | 115 | 345 | 418
Operating segments | Property and transportation | Property and Casualty Insurance |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Net earned premiums | 935 | 989 | 2,011 | 2,061
Losses and loss adjustment expenses | 728 | 784 | 1,426 | 1,441
Commissions and other underwriting expenses | 152 | 172 | 466 | 487
Property and casualty insurance underwriting profit | 55 | 33 | 119 | 133
Operating segments | Specialty casualty | Property and Casualty Insurance |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Net earned premiums | 810 | 797 | 2,403 | 2,371
Losses and loss adjustment expenses | 541 | 519 | 1,593 | 1,504
Commissions and other underwriting expenses | 236 | 215 | 708 | 657
Property and casualty insurance underwriting profit | 33 | 63 | 102 | 210
Operating segments | Specialty financial | Property and Casualty Insurance |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Net earned premiums | 268 | 269 | 826 | 754
Losses and loss adjustment expenses | 85 | 125 | 306 | 325
Commissions and other underwriting expenses | 132 | 123 | 394 | 350
Property and casualty insurance underwriting profit | 51 | 21 | 126 | 79
Operating segments | Other lines | Property and Casualty Insurance |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Losses and loss adjustment expenses | 1 | 2 | 2 | 4
Property and casualty insurance underwriting profit | $ (1) | $ (2) | $ (2) | $ (4)

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- Definition Underwriting income (loss) for the property and casualty insurance segment, which is calculated as premiums earned less losses and loss adjustment expenses less commissions and other underwriting expenses. + References No definition available. + Details
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- Definition Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 605 -Name Accounting Standards Codification -Section 55 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477548/944-605-55-14 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 605 -Name Accounting Standards Codification -Section 55 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477548/944-605-55-11 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 605 -Name Accounting Standards Codification -Section 55 -Paragraph 11 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477548/944-605-55-11 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479868/944-20-45-2 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1 + Details
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- Definition Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 605 -Name Accounting Standards Codification -Section 55 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477548/944-605-55-14 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 605 -Name Accounting Standards Codification -Section 55 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477548/944-605-55-11 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 605 -Name Accounting Standards Codification -Section 55 -Paragraph 15 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477548/944-605-55-15 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 605 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477548/944-605-55-12 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479838/944-20-50-1 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 605 -Name Accounting Standards Codification -Section 55 -Paragraph 11 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477548/944-605-55-11 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 235 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17(Column E)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477965/944-235-S99-2 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 605 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479032/944-605-50-1 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(13)(c)) -SubTopic 220 -Topic 942 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(1)) -SubTopic 220 -Topic 944 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1 + Details
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- Definition The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147476153/220-40-55-18 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org/1943274/2147476153/220-40-55-11 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147476153/220-40-55-4 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147476153/220-40-55-14 Reference 5: 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(4)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147476148/220-40-50-6 + Details
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