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Fair Value Measurements (Details Textual) $ in Millions | 3 Months Ended | 6 Months Ended |
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Jun. 30, 2015 USD ($) stock | Mar. 31, 2015 USD ($) | Jun. 30, 2014 USD ($) stock | Jun. 30, 2015 USD ($) stock professional | Jun. 30, 2014 USD ($) stock | Dec. 31, 2014 USD ($)
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
AFG's internal investment professionals | professional |  |  |  |  | 20 |  |
Level 3 assets as a percentage of total assets measured at fair value |  |  |  |  | 4.00% |  |
Percentage of level 3 assets that were priced using non-binding broker quotes |  |  |  |  | 72.00% |  |
Level 3 assets that were priced using non-binding broker quotes |  |  |  |  | $ 1,100 |  |
Percentage of internally developed Level 3 asset fair values to Shareholders' equity |  |  |  |  | 6.00% |  |
Total realized/unrealized gains (losses) included in net income on liabilities still outstanding |  |  |  | $ 1 |  | $ 5 |
Life contingent annuities |  | $ 201 |  |  | $ 201 |  | $ 203
Maximum [Member] |  |  |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
Percentage of internally developed Level 3 asset fair values to total assets (are less than) |  |  |  |  | 1.00% |  |
Fixed-indexed annuties (embedded derivative), majority of future years [Member] | Minimum [Member] |  |  |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
Unobservable input surrenders used in Level 3 fair value determination |  |  |  |  | 5.00% |  |
Fixed-indexed annuties (embedded derivative), majority of future years [Member] | Maximum [Member] |  |  |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
Unobservable input surrenders used in Level 3 fair value determination |  |  |  |  | 11.00% |  |
Fixed-indexed annuities (embedded derivative) [Member] |  |  |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
Fair value of derivatives in annuity benefits accumulated measured using a discounted cash flow approach |  | $ 1,260 |  |  | $ 1,260 |  |
Fixed-indexed annuities (embedded derivative) [Member] | Minimum [Member] |  |  |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
Unobservable input surrenders used in Level 3 fair value determination |  |  |  |  | 4.00% |  |
Fixed-indexed annuities (embedded derivative) [Member] | Maximum [Member] |  |  |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
Unobservable input surrenders used in Level 3 fair value determination |  |  |  |  | 16.00% |  |
Common stocks [Member] |  |  |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
Number of stocks transferred from Level 2 to Level 1 | stock |  | 5 |  |  | 6 |  |
Fair value of assets transferred from Level 2 to Level 1, during the second quarter |  | $ 26 |  |  |  |  |
Fair value of assets transferred from Level 2 to Level 1, during the first six months |  | $ 79 |  |  | $ 79 |  |
Perpetual preferred stocks [Member] |  |  |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
Number of stocks transferred from Level 2 to Level 1 | stock |  | 2 |  |  | 4 |  |
Fair value of assets transferred from Level 2 to Level 1, during the second quarter |  | $ 14 |  |  |  |  |
Fair value of assets transferred from Level 2 to Level 1, during the first six months |  | $ 19 |  |  | $ 19 |  |
Number of stocks transferred from Level 1 to Level 2 | stock |  |  |  | 1 |  | 9 |
Fair value of assets transferred from Level 1 to Level 2, during the first six months |  |  |  | $ 55 |  | $ 55 |
Perpetual preferred stocks [Member] | Maximum [Member] |  |  |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
Fair value of assets transferred from Level 1 to Level 2, during the second quarter (are less than) |  |  |  | $ 1 |  |  |
Mandatory redeemable preferred stocks [Member] |  |  |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
Number of stocks transferred from Level 2 to Level 1 | stock |  | 1 |  |  | 1 |  |
Fair value of assets transferred from Level 2 to Level 1, during the second quarter |  | $ 10 |  |  |  |  |
Fair value of assets transferred from Level 2 to Level 1, during the first six months |  | $ 10 |  |  | $ 10 |  |
Run-off long-term care insurance business [Member] |  |  |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |  |  |
Estimated sale proceeds of the run-off long-term care insurance business | [1] |  | $ 14 |  |  |  |
[1] | Includes fair value of the potential additional consideration and is shown net of estimated expenses.

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