XML 66 R49.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Fair Value Measurements - Narrative (Details) $ in Millions |  | 12 Months Ended
--- | --- | ---
Dec. 24, 2015 USD ($) | Dec. 31, 2017 USD ($) professional | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |
AFG's internal investment professionals | professional |  |  | 25 |  |
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 |  |  | 79.00% |  |
Level 3 assets that were priced using non-binding broker quotes |  |  | $ 1,800 |  |
Life contingent annuities |  |  | $ 206 | $ 204 |
Maximum |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |
Percentage of internally developed Level 3 asset fair values to Shareholders' equity (are less than) |  |  | 10.00% |  |
Fixed-indexed annuities (embedded derivative) |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |
Fair value of derivatives in annuity benefits accumulated measured using a discounted cash flow approach |  |  | $ 2,540 |  |
Fixed-indexed annuities (embedded derivative) | Minimum |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |
Unobservable input surrenders used in Level 3 fair value determination |  |  | 3.00% |  |
Fixed-indexed annuities (embedded derivative) | Maximum |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |
Unobservable input surrenders used in Level 3 fair value determination |  |  | 23.00% |  |
Fixed-indexed annuities (embedded derivative), majority of future years | Minimum |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |
Unobservable input surrenders used in Level 3 fair value determination |  |  | 6.00% |  |
Fixed-indexed annuities (embedded derivative), majority of future years | Maximum |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |
Unobservable input surrenders used in Level 3 fair value determination |  |  | 10.00% |  |
Not Designated as Hedging Instrument | Annuity benefits | Fixed-indexed annuities (embedded derivative) |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |
Total realized/unrealized gains (losses) included in net income for the embedded derivatives related to the unlocking of actuarial assumptions |  |  | $ (25) | $ (17) | $ (28)
Run-off long-term care insurance business |  |  |  |  |
Fair Value Measurements (Textual) [Abstract] |  |  |  |  |
Net sale proceeds of the run-off long-term care insurance business | [1] | $ 13 |  |  |
[1] | Includes the fair value of the potential additional consideration and capital maintenance agreement and is shown net of estimated expenses.

X
- Definition Amount of increase (decrease) in the fair value of derivatives related to unlocking of actuarial assumptions recognized in the income statement. + References No definition available. + Details
Name: | afg_DerivativeGainLossOnDerivativeAnnuityUnlocking
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The net proceeds associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period. + References No definition available. + Details
Name: | afg_DisposalGroupProceedsfromDivestitureofBusinessesNet
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Risk associated with risk of surrenders, expressed as a percentage, used as an input to measure fair value. + References No definition available. + Details
Name: | afg_FairValueInputsSurrenders
Namespace Prefix: | afg_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair Value Measurements. + References No definition available. + Details
Name: | afg_FairValueMeasurementsTextualAbstract
Namespace Prefix: | afg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Level Three Asset As Percentage Of Asset Measured At Fair Value. + References No definition available. + Details
Name: | afg_LevelThreeAssetAsPercentageOfAssetMeasuredAtFairValue
Namespace Prefix: | afg_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Level three assets that were priced using non-binding broker quotes. + References No definition available. + Details
Name: | afg_LevelThreeAssetsThatWerePricedUsingNonBindingBrokerQuotes
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Financial liabilities on annuities in the payout phase that are contingent on the survival of the annuitant(s). + References No definition available. + Details
Name: | afg_LifeContingentAnnuities
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Number of internal investment professionals. + References No definition available. + Details
Name: | afg_NumberOfInternalInvestmentProfessionals
Namespace Prefix: | afg_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of Internally Developed Level 3 Assets to Total Shareholders' Equity + References No definition available. + Details
Name: | afg_PercentageOfInternallyDevelopedLevelThreeAssetsToShareholdersEquity
Namespace Prefix: | afg_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of level 3 assets that were priced using non-binding broker quotes. + References No definition available. + Details
Name: | afg_PercentageOfLevelThreeAssetsThatWerePricedUsingNonBindingBrokerQuotes
Namespace Prefix: | afg_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226008-175313 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13495-108611 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 + Details
Name: | us-gaap_DerivativeLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=afg_FixedIndexedAnnuitiesEmbeddedDerivativeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=afg_FixedIndexedAnnuitiesEmbeddedDerivativeMajorityofFutureYearsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=afg_AnnuitybenefitsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=afg_DisposalGroupsIncludingDiscontinuedOperationsLongtermCareBusinessMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |