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Fair Value Measurements - Narrative (Details) $ in Millions | 6 Months Ended |
--- | --- | ---
Jun. 30, 2020 USD ($) basispoint professional security | Dec. 31, 2019 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
AFG's internal investment professionals | professional | 20 |
Level 3 assets as a percentage of total assets measured at fair value | 7.00% |
Percentage of level 3 assets that were priced using non-binding broker quotes | 37.00% |
Level 3 assets that were priced using non-binding broker quotes | $ | $ 1,400 |
Percent of spreads between 200 and 700 basis points | 70.00% |
Life contingent annuities | $ | $ 255 | $ 247
Fixed-indexed and variable-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 | 7.00% |
Fixed-indexed and variable-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 | 10.00% |
Fixed-indexed and variable-indexed annuities (embedded derivative) |  |
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 | $ | $ 3,680 |
Embedded Derivative Financial Instruments [Member] | Minimum |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Unobservable input surrenders used in Level 3 fair value determination | 4.00% |
Embedded Derivative Financial Instruments [Member] | Maximum |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Unobservable input surrenders used in Level 3 fair value determination | 21.00% |
Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Internally developed level 3 assets | $ | $ 1,870 |
Third party pricing model | Fixed maturities | Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Internally developed level 3 assets | $ | $ 736 |
Securities priced using a third-party model | security | 41 |
Basis points credit spread applied by management using third party model | basispoint | 389 |
Third party pricing model | Fixed maturities | Level 3 | Minimum |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Basis points credit spread applied by management using third party model | basispoint | 200 |
Third party pricing model | Fixed maturities | Level 3 | Maximum |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Basis points credit spread applied by management using third party model | basispoint | 700 |
Credit spread used in pricing model | Third party pricing model | Fixed maturities | Level 3 | Minimum |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Basis points credit spread applied by management using third party model | basispoint | 53 |
Credit spread used in pricing model | Third party pricing model | Fixed maturities | Level 3 | Maximum |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Basis points credit spread applied by management using third party model | basispoint | 1,253 |

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