| **Condensed Financial Statements Of Parent Company Condensed Statements Of Income (Details) - USD ($) $ in Millions** | 3 Months Ended | 12 Months Ended |
|-----------------------------------------------------------------------------------------------------------------------|----------------|-----------------|
||
| **Revenues**                                                                                                          |           |            |   |   |   |   |   |   |   |   |   |
| Investment income, net of expenses                                                                                    |           |            |   |   |   |   |   |   | $ 619 | $ 609 | $ 595 |
| Investment gains and losses, net                                                                                      |           |            |   |   |   |   |   |   | (402) | 148 | 124 |
| Other revenues                                                                                                        |           |            |   |   |   |   |   |   | 5 | 5 | 5 |
| Total revenues                                                                                                        | $ 710          | $ 1,915         | $ 1,558 | $ 1,224 | $ 1,411 | $ 1,412 | $ 1,386 | $ 1,523 | 5,407 | 5,732 | 5,449 |
| **Expenses**                                                                                                          |           |            |   |   |   |   |   |   |   |   |   |
| Interest expense                                                                                                      |           |            |   |   |   |   |   |   | 53 | 53 | 53 |
| Other expenses                                                                                                        |           |            |   |   |   |   |   |   | 16 | 13 | 12 |
| Total expenses                                                                                                        |           |            |   |   |   |   |   |   | 5,156 | 5,002 | 4,637 |
| Income (Loss) Before Income Taxes and Earnings of Subsidiaries                                                        | (581)          | 618             | 264 | (50) | 197 | 129 | 128 | 276 | 251 | 730 | 812 |
| Benefit for income taxes                                                                                              |           |            |   |   |   |   |   |   | (36) | (315) | 221 |
| Net Income                                                                                                            | $ (452)        | $ 553           | $ 217 | $ (31) | $ 642 | $ 102 | $ 100 | $ 201 | 287 | 1,045 | 591 |
| Cincinnati Financial Corporation                                                                                      |           |            |   |   |   |   |   |   |   |   |   |
| **Revenues**                                                                                                          |           |            |   |   |   |   |   |   |   |   |   |
| Investment income, net of expenses                                                                                    |           |            |   |   |   |   |   |   | 65 | 62 | 56 |
| Investment gains and losses, net                                                                                      |           |            |   |   |   |   |   |   | (108) | 28 | 27 |
| Other revenues                                                                                                        |           |            |   |   |   |   |   |   | 15 | 15 | 15 |
| Total revenues                                                                                                        |           |            |   |   |   |   |   |   | (28) | 105 | 98 |
| **Expenses**                                                                                                          |           |            |   |   |   |   |   |   |   |   |   |
| Interest expense                                                                                                      |           |            |   |   |   |   |   |   | 52 | 52 | 52 |
| Other expenses                                                                                                        |           |            |   |   |   |   |   |   | 31 | 28 | 27 |
| Total expenses                                                                                                        |           |            |   |   |   |   |   |   | 83 | 80 | 79 |
| Income (Loss) Before Income Taxes and Earnings of Subsidiaries                                                        |           |            |   |   |   |   |   |   | (111) | 25 | 19 |
| Benefit for income taxes                                                                                              |           |            |   |   |   |   |   |   | (31) | (161) | (6) |
| Net Income (Loss) Before Earnings of Subsidiaries                                                                     |           |            |   |   |   |   |   |   | (80) | 186 | 25 |
| Increase in equity of subsidiaries                                                                                    |           |            |   |   |   |   |   |   | 367 | 859 | 566 |
| Net Income                                                                                                            |           |            |   |   |   |   |   |   | $ 287 | $ 1,045 | $ 591 |

| X                                                                                                                                                                                                                                                                           |
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Income Loss Before Equity Method Investments
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Increase or decrease in equity subsidiaries.
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| - Definition
The total amount of expense recognized during the period for future policy benefits, claims and claims adjustment costs, and for selling, general and administrative costs.
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| - Definition
Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.
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| - Definition
Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.
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| - Definition
Amount of the cost of borrowed funds accounted for as interest expense.
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| - Definition
The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.
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| - Definition
Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.
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| - Definition
The total amount of other operating cost and expense items that are associated with the entity's normal revenue producing operation.
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Amount of revenue and income classified as other.
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| - Definition
The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.
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| - Definition
Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).
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