| **Summary Of Significant Accounting Policies (Narrative) (Details)**                                                      | 12 Months Ended   |
|---------------------------------------------------------------------------------------------------------------------------|-------------------|
||
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Income Tax Examination, Penalties Expense                                                                                 | $ 0               |   |   |   |
| Number of operating subsidaries | subsidiary                                                                              | 2                 |   |   |   |
| Number of independent insurance agencies | independent_insurance_agency                                                   | 1,984             |   |   |   |
| Number of reporting locations | reporting_locations                                                                       | 2,861             |   |   |   |
| Number of states in which entity operates | state                                                                         | 46                |   |   |   |
| Excess (deficit) of Separate Account Fair Value over (under) Contract Holder Account Value                                | $ (64,000,000)    | $ 79,000,000 |   |   |
| Other invested assets                                                                                                     | 452,000,000       | 329,000,000 |   |   |
| Depreciation expense                                                                                                      | 33,000,000        | 33,000,000 | $ 33,000,000 |   |
| Land, building and equipment impairments                                                                                  | 0                 | 0 | 0 |   |
| Premium Receivable, Allowance for Credit Loss                                                                             | 13,000,000        | 14,000,000 | 19,000,000 |   |
| Premium Receivable, Allowance for Credit Loss, Property Casualty Premiums Receivable                                      |              |   | 9,000,000 |   |
| Covid-19 pandemic-related incurred loss and expenses                                                                      |              |   | $ 85,000,000 |   |
| Minimum participant age to elect                                                                                          |              |   |   | 40 years |
| Accounting Standards Update 2018-12                                                                                       |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest                                           | $ 30,000,000      |   |   |   |
| Minimum [Member]                                                                                                          |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Estimated useful lives                                                                                                    | 3 years           |   |   |   |
| Maximum                                                                                                                   |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Estimated useful lives                                                                                                    | 39 years 6 months |   |   |   |
| Life Policy Loans                                                                                                         |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Other invested assets                                                                                                     | $ 31,000,000      | 31,000,000 |   |   |
| Venture Capital Funds                                                                                                     |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Other invested assets                                                                                                     | 337,000,000       | 227,000,000 |   |   |
| Real Estate Investment                                                                                                    |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Other invested assets                                                                                                     | 47,000,000        | 36,000,000 |   |   |
| Other than Securities Investment                                                                                          |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Other invested assets                                                                                                     | $ 37,000,000      | $ 35,000,000 |   |   |
| 10 Largest States                                                                                                         |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Percentage Of Premiums                                                                                                    | 50.10%            | 52.10% |   |   |
| Ohio, Largest State                                                                                                       |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Percentage Of Premiums                                                                                                    | 13.40%            | 14.40% |   |   |
| Illinois, New York, North Carolina, Pennsylvania, Georgia and Indiana | Minimum [Member]                                  |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Percentage Of Premiums                                                                                                    | 4.00%             |   |   |   |
| Illinois, New York, North Carolina, Pennsylvania, Georgia and Indiana | Maximum                                           |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Percentage Of Premiums                                                                                                    | 6.00%             |   |   |   |
| Largest Single Agency Relationship                                                                                        |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Percentage Of Premiums                                                                                                    | 0.60%             |   |   |   |
| All Other | Maximum                                                                                                       |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Percentage Of Premiums                                                                                                    | 5.00%             |   |   |   |
| Stock Options                                                                                                             |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Weighted-average remaining contractual life for options expected to vest                                                  | 10 years          |   |   |   |
| Property Casualty Insurance Segment                                                                                       |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Number of operating subsidaries | subsidiary                                                                              | 2                 |   |   |   |
| Stock Options                                                                                                             |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Awards vesting period                                                                                                     | 3 years           |   |   |   |
| Restricted Stock Units (RSUs)                                                                                             |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Awards vesting period                                                                                                     | 3 years           |   |   |   |
| Cincinnati Global                                                                                                         |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Goodwill                                                                                                                  | $ 30,000,000      | $ 30,000,000 |   |   |
| Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets | $ 31,000,000      | $ 31,000,000 |   |   |
| Broker Relationships and Internally developed technology | Cincinnati Global | Minimum [Member]                           |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Useful life                                                                                                               | 5 years           |   |   |   |
| Broker Relationships and Internally developed technology | Cincinnati Global | Maximum                                    |              |   |   |   |
| **Significant Accounting Policies**                                                                                       |              |   |   |   |
| Useful life                                                                                                               | 15 years          |   |   |   |

| X                                                                                                                                                                                                                                                                                        |
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| - Definition
Covid-19 pandemic-related incurred loss and expenses
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Age at which participants could elect to remain in the defined benefit plan as of August 31, 2008.
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Amount that Separate Account Fair Value is greater (less) than the Contract Holder's Account Value
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Independent Insurance Agencies and Brokerages
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Number of Locations
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Number of Subsidiaries
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Percentage of earned premiums.
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Premium Receivable, Allowance for Credit Loss, Property Casualty Premiums Receivable
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Significant Accounting Policies [Line Items]
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| - Definition
Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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| - Definition
Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.
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| - Definition
Amount of assets, excluding financial assets and goodwill, that lack physical substance, having a projected indefinite period of benefit, acquired at the acquisition date.
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| - Definition
The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.
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| - Definition
Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.
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| - Definition
The amount of estimated penalties recognized in the period arising from income tax examinations.
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| - Definition
The number of states the entity operates in as of the balance sheet date.
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| - Definition
Amount of investments classified as other.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The carrying value as of the balance sheet date of the estimated valuation allowance to reduce gross premiums receivable to net realizable value.
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| - Definition
Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.
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| - Definition
Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.
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| - Definition
Weighted average remaining contractual term of exercisable stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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| - Definition
Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.
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