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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
--- | ---
Mar. 31, 2026 | Mar. 31, 2025
Segment Reporting Information [Line Items] |  |
Net earned premiums | $ 1,609 | $ 1,580
Losses and loss adjustment expenses | 906 | 965
Commissions and other underwriting expenses | 556 | 530
Operating segments | Property and Casualty Insurance |  |
Segment Reporting Information [Line Items] |  |
Net earned premiums | 1,609 | 1,580
Losses and loss adjustment expenses | 906 | 965
Commissions and other underwriting expenses | 547 | 521
Property and casualty insurance underwriting profit | 156 | 94
Operating segments | Property and transportation | Property and Casualty Insurance |  |
Segment Reporting Information [Line Items] |  |
Net earned premiums | 526 | 500
Losses and loss adjustment expenses | 301 | 311
Commissions and other underwriting expenses | 160 | 152
Property and casualty insurance underwriting profit | 65 | 37
Operating segments | Specialty casualty | Property and Casualty Insurance |  |
Segment Reporting Information [Line Items] |  |
Net earned premiums | 799 | 794
Losses and loss adjustment expenses | 517 | 536
Commissions and other underwriting expenses | 248 | 238
Property and casualty insurance underwriting profit | 34 | 20
Operating segments | Specialty financial | Property and Casualty Insurance |  |
Segment Reporting Information [Line Items] |  |
Net earned premiums | 284 | 286
Losses and loss adjustment expenses | 88 | 118
Commissions and other underwriting expenses | 139 | 131
Property and casualty insurance underwriting profit | $ 57 | $ 37

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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 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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