| **Condensed Financial Statements Of Parent Company Condensed Statements Of Comprehensive Income (Details) - USD ($) $ in Millions** | 3 Months Ended | 12 Months Ended |
|-------------------------------------------------------------------------------------------------------------------------------------|----------------|-----------------|
||
| **Condensed Financial Statements, Captions**                                                                                        |           |            |   |   |   |   |   |   |   |   |   |
| Net Income                                                                                                                          | $ (452)        | $ 553           | $ 217 | $ (31) | $ 642 | $ 102 | $ 100 | $ 201 | $ 287 | $ 1,045 | $ 591 |
| Unrealized gains and (losses) on investments available for sale                                                                     |           |            |   |   |   |   |   |   | (267) | 598 | 345 |
| Unrealized gains and (losses) on investments available for sale, investments held by subsidiaries and other                         |           |            |   |   |   |   |   |   | (330) | 914 | 521 |
| Amortization of pension actuarial gains (losses) and prior service cost                                                             |           |            |   |   |   |   |   |   | (4) | 14 | 16 |
| OCI                                                                                                                                 |           |            |   |   |   |   |   |   | (334) | 928 | 537 |
| Income taxes on above of other comprehensive income (loss)                                                                          |           |            |   |   |   |   |   |   | (71) | 325 | 188 |
| Other comprehensive income (loss), net of tax                                                                                       |           |            |   |   |   |   |   |   | (263) | 603 | 349 |
| Comprehensive Income                                                                                                                |           |            |   |   |   |   |   |   | 24 | 1,648 | 940 |
| Cincinnati Financial Corporation                                                                                                    |           |            |   |   |   |   |   |   |   |   |   |
| **Condensed Financial Statements, Captions**                                                                                        |           |            |   |   |   |   |   |   |   |   |   |
| Net Income                                                                                                                          |           |            |   |   |   |   |   |   | 287 | 1,045 | 591 |
| Unrealized gains and (losses) on investments available for sale                                                                     |           |            |   |   |   |   |   |   | (110) | 391 | 221 |
| Unrealized gains and (losses) on investments held by subsidiaries                                                                   |           |            |   |   |   |   |   |   | (631) | 672 | 434 |
| Reclassification adjustment for (gains) and losses included in net income                                                           |           |            |   |   |   |   |   |   | 108 | (28) | (27) |
| Reclassification adjustment for (gains) included in net income on subsidiaries                                                      |           |            |   |   |   |   |   |   | 294 | (120) | (97) |
| Unrealized (losses) and gains on other                                                                                              |           |            |   |   |   |   |   |   | 0 | (2) | (6) |
| Unrealized gains and (losses) on other subsidiaries                                                                                 |           |            |   |   |   |   |   |   | $ 9 | $ 1 | $ (4) |

| X                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI Held by Subsidiaries, before Tax
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Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, before Tax
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Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period Held by Subsidiaries and Other, before Tax
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No definition available.
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Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period Held by Subsidiaries, before Tax
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No definition available.
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Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Other Subsidiaries, before Tax
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.
+ References
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| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
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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, before tax, after reclassification adjustment, of (increase) decrease in accumulated other comprehensive (income) loss for defined benefit plan, attributable to parent entity.
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| - Definition
Amount before tax of other comprehensive income (loss) attributable to parent entity.
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| - Definition
Amount after tax and reclassification adjustments of other comprehensive income (loss).
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| - Definition
Amount of tax expense (benefit) allocated to other comprehensive income (loss) attributable to parent entity.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax and reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.
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