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Fair Value Measurements - Narrative (Details) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2019 USD ($) basispoint security professional stock | Mar. 31, 2018 USD ($) stock | Dec. 31, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
AFG's internal investment professionals | professional | 25 |  |
Number of stocks transferred from Level 1 to Level 2 | stock | 0 | 0 |
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 | 60.00% |  |
Level 3 assets that were priced using non-binding broker quotes | $ 2,200 |  |
Percent of spreads between 400 and 700 basis points | 80.00% |  |
Fair value of equity securities transferred into Level 3 | $ 16 | $ 36 |
Life contingent annuities | $ 238 |  | $ 232
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 | 11.00% |  |
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 | $ 3,250 |  |
Fixed-indexed and variable-indexed annuities (embedded derivative) | 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% |  |
Fixed-indexed and variable-indexed annuities (embedded derivative) | Maximum |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Unobservable input surrenders used in Level 3 fair value determination | 23.00% |  |
Level 3 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Internally developed level 3 assets | $ 1,230 |  |
Fixed maturities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Fair value of equity securities transferred into Level 3 | 0 | 7 |
Equity securities |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Fair value of equity securities transferred into Level 3 | 16 | $ 29 |
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 | $ 743 |  |
Securities priced using a third-party model | security | 120 |  |
Basis points credit spread applied by management using third party model | basispoint | 577 |  |
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 | 100 |  |
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 | 2,966 |  |
Maximum | Third party pricing model | Fixed maturities | Level 3 |  |  |
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 |  |
Minimum | Third party pricing model | Fixed maturities | Level 3 |  |  |
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 | 400 |  |

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