| **Summary of Investments Other Than Investments In Related Parties (Details) $ in Millions**                                   | Dec. 31, 2021 USD ($) |
|--------------------------------------------------------------------------------------------------------------------------------|-----------------------|
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | $ 16,680              |
| Fair value                                                                                                                     | 0                     |
| Balance sheet                                                                                                                  | 24,666                |
| Fixed Maturities                                                                                                               |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 12,230                |
| Fair value                                                                                                                     | 13,022                |
| Balance sheet                                                                                                                  | 13,022                |
| Equity Securities                                                                                                              |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 4,121                 |
| Fair value                                                                                                                     | 11,315                |
| Balance sheet                                                                                                                  | 11,315                |
| Other than Securities Investment                                                                                               |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 329                   |
| Fair value                                                                                                                     | 0                     |
| Balance sheet                                                                                                                  | 329                   |
| States, Municipalities and Political Subdivisions | Fixed Maturities                                                           |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 4,768                 |
| Fair value                                                                                                                     | 5,095                 |
| Balance sheet                                                                                                                  | 5,095                 |
| States, Municipalities and Political Subdivisions | Fixed Maturities | Cincinnati Financial Corporation                        |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 57                    |
| Fair value                                                                                                                     | 57                    |
| Balance sheet                                                                                                                  | 57                    |
| States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Insurance Company                        |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 3,343                 |
| Fair value                                                                                                                     | 3,583                 |
| Balance sheet                                                                                                                  | 3,583                 |
| States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Casualty Company                         |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 230                   |
| Fair value                                                                                                                     | 246                   |
| Balance sheet                                                                                                                  | 246                   |
| States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Indemnity Company                        |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 49                    |
| Fair value                                                                                                                     | 53                    |
| Balance sheet                                                                                                                  | 53                    |
| States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Life Insurance Company                   |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 446                   |
| Fair value                                                                                                                     | 471                   |
| Balance sheet                                                                                                                  | 471                   |
| States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Specialty Underwriters Insurance Company |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 643                   |
| Fair value                                                                                                                     | 685                   |
| Balance sheet                                                                                                                  | 685                   |
| United States Government | Fixed Maturities                                                                                    |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 121                   |
| Fair value                                                                                                                     | 123                   |
| Balance sheet                                                                                                                  | 123                   |
| United States Government | Fixed Maturities | The Cincinnati Insurance Company                                                 |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 69                    |
| Fair value                                                                                                                     | 71                    |
| Balance sheet                                                                                                                  | 71                    |
| United States Government | Fixed Maturities | The Cincinnati Casualty Company                                                  |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 1                     |
| Fair value                                                                                                                     | 1                     |
| Balance sheet                                                                                                                  | 1                     |
| United States Government | Fixed Maturities | The Cincinnati Indemnity Company                                                 |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 1                     |
| Fair value                                                                                                                     | 1                     |
| Balance sheet                                                                                                                  | 1                     |
| United States Government | Fixed Maturities | Cincinnati Global                                                                |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 50                    |
| Fair value                                                                                                                     | 50                    |
| Balance sheet                                                                                                                  | 50                    |
| Foreign Government | Fixed Maturities                                                                                          |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 26                    |
| Fair value                                                                                                                     | 26                    |
| Balance sheet                                                                                                                  | 26                    |
| Foreign Government | Fixed Maturities | The Cincinnati Insurance Company                                                       |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 10                    |
| Fair value                                                                                                                     | 10                    |
| Balance sheet                                                                                                                  | 10                    |
| Foreign Government | Fixed Maturities | Cincinnati Global                                                                      |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 16                    |
| Fair value                                                                                                                     | 16                    |
| Balance sheet                                                                                                                  | 16                    |
| Government-Sponsored Enterprises | Fixed Maturities                                                                            |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 8                     |
| Fair value                                                                                                                     | 8                     |
| Balance sheet                                                                                                                  | 8                     |
| Government-Sponsored Enterprises | Fixed Maturities | Cincinnati Global                                                        |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 8                     |
| Fair value                                                                                                                     | 8                     |
| Balance sheet                                                                                                                  | 8                     |
| All Other Corporate Bonds | Fixed Maturities                                                                                   |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 7,307                 |
| Fair value                                                                                                                     | 7,770                 |
| Balance sheet                                                                                                                  | 7,770                 |
| All Other Corporate Bonds | Fixed Maturities | Cincinnati Financial Corporation                                                |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 7                     |
| Fair value                                                                                                                     | 7                     |
| Balance sheet                                                                                                                  | 7                     |
| All Other Corporate Bonds | Fixed Maturities | The Cincinnati Insurance Company                                                |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 3,443                 |
| Fair value                                                                                                                     | 3,628                 |
| Balance sheet                                                                                                                  | 3,628                 |
| All Other Corporate Bonds | Fixed Maturities | The Cincinnati Casualty Company                                                 |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 102                   |
| Fair value                                                                                                                     | 106                   |
| Balance sheet                                                                                                                  | 106                   |
| All Other Corporate Bonds | Fixed Maturities | The Cincinnati Indemnity Company                                                |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 33                    |
| Fair value                                                                                                                     | 35                    |
| Balance sheet                                                                                                                  | 35                    |
| All Other Corporate Bonds | Fixed Maturities | The Cincinnati Life Insurance Company                                           |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 3,339                 |
| Fair value                                                                                                                     | 3,595                 |
| Balance sheet                                                                                                                  | 3,595                 |
| All Other Corporate Bonds | Fixed Maturities | The Cincinnati Specialty Underwriters Insurance Company                         |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 300                   |
| Fair value                                                                                                                     | 316                   |
| Balance sheet                                                                                                                  | 316                   |
| All Other Corporate Bonds | Fixed Maturities | Cincinnati Global                                                               |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 82                    |
| Fair value                                                                                                                     | 82                    |
| Balance sheet                                                                                                                  | 82                    |
| All Other Corporate Bonds | Fixed Maturities | CSU Producers Resources Inc.                                                    |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 1                     |
| Fair value                                                                                                                     | 1                     |
| Balance sheet                                                                                                                  | 1                     |
| Common Stock | Equity Securities                                                                                               |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 3,697                 |
| Fair value                                                                                                                     | 10,862                |
| Balance sheet                                                                                                                  | 10,862                |
| Common Stock | Equity Securities | Cincinnati Financial Corporation                                                            |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 1,656                 |
| Fair value                                                                                                                     | 4,774                 |
| Balance sheet                                                                                                                  | 4,774                 |
| Common Stock | Equity Securities | The Cincinnati Insurance Company                                                            |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 1,848                 |
| Fair value                                                                                                                     | 5,543                 |
| Balance sheet                                                                                                                  | 5,543                 |
| Common Stock | Equity Securities | The Cincinnati Casualty Company                                                             |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 59                    |
| Fair value                                                                                                                     | 186                   |
| Balance sheet                                                                                                                  | 186                   |
| Common Stock | Equity Securities | The Cincinnati Indemnity Company                                                            |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 18                    |
| Fair value                                                                                                                     | 44                    |
| Balance sheet                                                                                                                  | 44                    |
| Common Stock | Equity Securities | The Cincinnati Specialty Underwriters Insurance Company                                     |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 101                   |
| Fair value                                                                                                                     | 287                   |
| Balance sheet                                                                                                                  | 287                   |
| Common Stock | Equity Securities | CSU Producers Resources Inc.                                                                |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 15                    |
| Fair value                                                                                                                     | 28                    |
| Balance sheet                                                                                                                  | 28                    |
| Nonredeemable Preferred Stock | Equity Securities                                                                              |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 424                   |
| Fair value                                                                                                                     | 453                   |
| Balance sheet                                                                                                                  | 453                   |
| Nonredeemable Preferred Stock | Equity Securities | Cincinnati Financial Corporation                                           |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 4                     |
| Fair value                                                                                                                     | 4                     |
| Balance sheet                                                                                                                  | 4                     |
| Nonredeemable Preferred Stock | Equity Securities | The Cincinnati Insurance Company                                           |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 407                   |
| Fair value                                                                                                                     | 436                   |
| Balance sheet                                                                                                                  | 436                   |
| Nonredeemable Preferred Stock | Equity Securities | The Cincinnati Life Insurance Company                                      |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 13                    |
| Fair value                                                                                                                     | 13                    |
| Balance sheet                                                                                                                  | 13                    |
| Policy Loans | Other than Securities Investment | The Cincinnati Life Insurance Company                                        |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 31                    |
| Fair value                                                                                                                     | 0                     |
| Balance sheet                                                                                                                  | 31                    |
| Lloyd's and other deposits | Other than Securities Investment | Cincinnati Financial Corporation                               |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 6                     |
| Fair value                                                                                                                     | 0                     |
| Balance sheet                                                                                                                  | 6                     |
| Lloyd's and other deposits | Other than Securities Investment | Cincinnati Global                                              |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 29                    |
| Fair value                                                                                                                     | 0                     |
| Balance sheet                                                                                                                  | 29                    |
| Limited Partnership | Other than Securities Investment | Cincinnati Financial Corporation                                      |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 36                    |
| Fair value                                                                                                                     | 0                     |
| Balance sheet                                                                                                                  | 36                    |
| Limited Partnership | Other than Securities Investment | The Cincinnati Insurance Company                                      |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 191                   |
| Balance sheet                                                                                                                  | 191                   |
| Real Estate | Other than Securities Investment | Cincinnati Financial Corporation                                              |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 4                     |
| Balance sheet                                                                                                                  | 4                     |
| Real Estate | Other than Securities Investment | The Cincinnati Insurance Company                                              |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 27                    |
| Balance sheet                                                                                                                  | 27                    |
| Real Estate | Other than Securities Investment | The Cincinnati Life Insurance Company                                         |                  |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                  |
| Cost or amortized cost                                                                                                         | 5                     |
| Balance sheet                                                                                                                  | $ 5                   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| - Definition
Amount of investment held by insurance company, excluding investment in related party.
+ References
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| - Definition
Cost of investment held by insurance company, excluding investment in related party.
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| - Definition
Fair value of investment held by insurance company, excluding investment in related party.
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