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Investments (Details 1) (USD $) In Millions, unless otherwise specified | Mar. 31, 2015 | Dec. 31, 2014
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U.S. Government and government agencies [Member] |  |
Available for sale securities in a continuous unrealized loss position |  |
Unrealized Loss - Less than twelve months | $ 0 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember | $ 0 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember
Fair Value - Less than twelve months | 6 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember | 39 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember
Fair Value as % of Cost - Less than twelve months | 100.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember | 100.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember
Unrealized Loss - Twelve months or more | (3)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember | (2)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember
Fair Value - Twelve months or more | 15 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember | 15 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember
Fair Value as % of Cost - Twelve months or more | 83.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember | 88.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember
States, municipalities and political subdivisions [Member] |  |
Available for sale securities in a continuous unrealized loss position |  |
Unrealized Loss - Less than twelve months | (5)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember | (2)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Fair Value - Less than twelve months | 507 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember | 222 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Fair Value as % of Cost - Less than twelve months | 99.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember | 99.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Unrealized Loss - Twelve months or more | (3)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember | (8)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Fair Value - Twelve months or more | 57 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember | 408 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Fair Value as % of Cost - Twelve months or more | 95.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember | 98.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Residential Mortgage Backed Securities [Member] |  |
Available for sale securities in a continuous unrealized loss position |  |
Unrealized Loss - Less than twelve months | (5)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember | (4)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember
Fair Value - Less than twelve months | 332 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember | 298 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember
Fair Value as % of Cost - Less than twelve months | 99.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember | 99.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember
Unrealized Loss - Twelve months or more | (8)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember | (11)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember
Fair Value - Twelve months or more | 193 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember | 209 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember
Fair Value as % of Cost - Twelve months or more | 96.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember | 95.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember
Commercial Mortgage Backed Securities [Member] |  |
Available for sale securities in a continuous unrealized loss position |  |
Unrealized Loss - Less than twelve months | 0 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | (1)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember
Fair Value - Less than twelve months | 38 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 38 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember
Fair Value as % of Cost - Less than twelve months | 100.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 97.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember
Unrealized Loss - Twelve months or more | 0 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 0 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember
Fair Value - Twelve months or more | 10 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 11 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember
Fair Value as % of Cost - Twelve months or more | 100.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 100.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember
Asset-backed Securities [Member] |  |
Available for sale securities in a continuous unrealized loss position |  |
Unrealized Loss - Less than twelve months | (3)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | (11)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Fair Value - Less than twelve months | 625 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 1,389 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Fair Value as % of Cost - Less than twelve months | 100.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 99.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Unrealized Loss - Twelve months or more | (5)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | (11)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Fair Value - Twelve months or more | 461 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 622 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Fair Value as % of Cost - Twelve months or more | 99.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 98.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
All other corporate [Member] |  |
Available for sale securities in a continuous unrealized loss position |  |
Unrealized Loss - Less than twelve months | (18)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember | (16)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember
Fair Value - Less than twelve months | 555 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember | 588 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember
Fair Value as % of Cost - Less than twelve months | 97.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember | 97.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember
Unrealized Loss - Twelve months or more | (4)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember | (13)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember
Fair Value - Twelve months or more | 75 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember | 433 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember
Fair Value as % of Cost - Twelve months or more | 95.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember | 97.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember
Fixed maturities [Member] |  |
Available for sale securities in a continuous unrealized loss position |  |
Unrealized Loss - Less than twelve months | (31)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember | (34)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember
Fair Value - Less than twelve months | 2,063 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember | 2,574 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember
Fair Value as % of Cost - Less than twelve months | 99.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember | 99.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember
Unrealized Loss - Twelve months or more | (23)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember | (45)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember
Fair Value - Twelve months or more | 811 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember | 1,698 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember
Fair Value as % of Cost - Twelve months or more | 97.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember | 97.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_FixedMaturitiesMember
Common stocks [Member] |  |
Available for sale securities in a continuous unrealized loss position |  |
Unrealized Loss - Less than twelve months | (33)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember | (25)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember
Fair Value - Less than twelve months | 218 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember | 260 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember
Fair Value as % of Cost - Less than twelve months | 87.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember | 91.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember
Unrealized Loss - Twelve months or more | 0 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember | 0 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember
Fair Value - Twelve months or more | 0 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember | 0 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember
Fair Value as % of Cost - Twelve months or more | 0.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember | 0.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommonStockMember
Perpetual preferred stocks [Member] |  |
Available for sale securities in a continuous unrealized loss position |  |
Unrealized Loss - Less than twelve months | 0 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember | (1)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember
Fair Value - Less than twelve months | 20 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember | 45 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember
Fair Value as % of Cost - Less than twelve months | 100.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember | 98.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember
Unrealized Loss - Twelve months or more | (3)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember | (4)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember
Fair Value - Twelve months or more | $ 49 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember | $ 55 us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember
Fair Value as % of Cost - Twelve months or more | 94.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember | 93.00%afg_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueAsPercentageOfCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PreferredStockMember

X
- Definition Available for sale securities continuous unrealized loss position less than twelve months fair value as percentage of cost. + References No definition available. + Details
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- Definition Available for sale securities continuous unrealized loss position twelve months or longer fair value as percentage of cost. + References No definition available. + Details
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- Definition Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 + Details
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