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Fair Value Measurements - Narrative (Details) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2021 USD ($) professional | Dec. 31, 2020 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
AFG's internal investment professionals | professional | 20 |
Life contingent annuities | $ 1,120 | $ 1,110
Embedded derivatives | Minimum |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Unobservable input surrenders used in Level 3 fair value determination | 7.00% |
Embedded derivatives | Maximum |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Unobservable input surrenders used in Level 3 fair value determination | 22.00% |
Fixed-Indexed Annuities (Embedded Derivative) | Liabilities of discontinued annuity operations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Fair value of derivatives in annuity benefits accumulated measured using a discounted cash flow approach | $ 3,950 |
Fixed-Indexed Annuities (Embedded Derivative), Majority of Future Years | Minimum |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Unobservable input surrenders used in Level 3 fair value determination | 8.00% |
Fixed-Indexed Annuities (Embedded Derivative), Majority of Future Years | Maximum |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Unobservable input surrenders used in Level 3 fair value determination | 11.00% |
Level 3 | Continuing operations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Level 3 assets as a percentage of total assets measured at fair value | 5.00% |
Percentage of level 3 assets that were priced using non-binding broker quotes | 22.00% |
Level 3 assets that were priced using non-binding broker quotes | $ 185 |
Level three assets that were priced by pricing services. | $ 78 |
Percentage Of Level Three Assets That Were Priced By Pricing Services | 9.00% |
Internally developed level 3 assets | $ 488 |
Percentage Of Internally Developed Level Three Assets Compared to Total Level 3 Assets | 58.00% |

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