| **Note Payable**                      | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
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| **Notes Payable, Current [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Note Payable                          | Note PayableWe have one unsecured revolving credit facility through multiple commercial banks that expires on February 4, 2026. The borrowing capacity is $300 million with an additional $300 million accordion feature. Terms and conditions of the agreement include a debt-to-total capital maximum of 35%. We had no compensating balance requirements on short-term debt for either 2022 or 2021. The line of credit had $50 million and $54 million drawn at December 31, 2022 and 2021, respectively. The interest rate charged on our borrowings on this credit agreement ranged from 0.99% to 5.00% during 2022 and ranged from 0.97% to 1.03% during 2021. In addition, we have letters of credit related to our Cincinnati Re and Cincinnati Global operations with no amounts drawn at December 31, 2022 and 2021. |

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| - Definition
The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.
+ References
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