XML 108 R93.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Insurance - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2018 | Sep. 30, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2016 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Insurance [Line Items] |  |  |  |  |  |  |  |
Carrying value of cash and securities owned by U.S.-based insurance subsidiaries on deposit | $ 1,060 |  |  |  |  | $ 1,060 |  |
Carrying value of cash and securities owned by insurance subsidiaries on deposit in support of underwriting activities at Lloyd's | 118 |  |  |  |  | 118 |  |
Undrawn letters of credit | 296 |  |  |  |  | 296 |  |
Undrawn letters of credit, collateralized | 0 |  |  |  |  | $ 0 |  |
Workers' compensation insurance discount rate |  |  |  |  |  | 4.50% | 4.50% |
Workers' compensation insurance discount, which has reduced the liability for unpaid losses and loss adjustment expenses | 13 |  | $ 15 |  |  | $ 13 | $ 15 |
Long-term care insurance reserves, net of reinsurance recoverables | 45 |  | 39 |  |  | 45 | 39 |
Investment in Federal Home Loan Bank capital stock | 47 |  |  |  |  | 47 |  |
Advances from Federal Home Loan Bank | 1,100 |  |  |  |  | $ 1,100 |  |
Proceeds from Federal Home Loan Bank Advance, Investing Activities | 225 |  |  |  |  |  |  |
Description of variable rate basis |  |  |  |  |  | LIBOR |  |
Repayments of advances from Federal Home Loan Bank due in next twelve months | 445 |  |  |  |  | $ 445 |  |
Repayments of advances from Federal Home Loan Bank due in year two | 40 |  |  |  |  | 40 |  |
Repayments of advances from Federal Home Loan Bank due in year three | 611 |  |  |  |  | 611 |  |
Fair value of fixed maturity investments held as collateral by the Federal Home Loan Bank | 1,280 |  |  |  |  | 1,280 |  |
Interest on advances from Federal Home Loan Bank |  |  |  |  |  | 20 | 14 | $ 8
Maximum amount of dividends available to be paid by insurance subsidiaries to AFG without prior approval of regulatory authorities | 1,300 |  |  |  |  | 1,300 |  |
Dividends on common stock |  |  |  |  |  | (397) | (421) | (187)
Aggregate guaranteed minimum death benefit value on variable annuity polices in force | 35 |  | 15 |  |  | $ 35 | 15 |
Minimum | LIBOR |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
FHLB advances, basis spread on variable rate |  |  |  |  |  | 0.15% |  |
Maximum |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Dividends payments without violating the most restrictive debt covenants, minimum | 2,000 |  |  |  |  | $ 2,000 |  |
Maximum | LIBOR |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
FHLB advances, basis spread on variable rate |  |  |  |  |  | 0.24% |  |
Average | LIBOR |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
FHLB advances, basis spread on variable rate |  |  |  |  |  | 2.68% |  |
FHLB, advances, refinanced terms |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Advances from Federal Home Loan Bank | 40 |  | 831 |  |  | $ 40 | 831 |
Catastrophe Bonds |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Catastrophe reinsurance coverage, excess retention percentage |  |  |  |  |  | 95.00% |  |
Catastrophe reinsurance coverage, excess retention amount |  |  |  |  |  | $ 200 |  |
Catastrophe reinsurance coverage, retention amount |  |  |  |  |  | 104 |  |
Catastrophe reinsurance coverage, annual cost |  |  |  |  |  | 11 |  |
Life insurance |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Increased statutory surplus resulting from reinsurance treaty | 2,701 |  | 2,132 |  |  | 2,701 | 2,132 |
Life insurance in force, ceded premiums | 7,690 |  | 8,320 |  |  | 7,690 | 8,320 |
Life insurance in force, direct premiums | 10,820 |  | 12,050 |  |  | 10,820 | 12,050 |
Reinsurance ceded |  |  |  |  |  | 22 | 28 | 31
Reinsurance recoveries |  |  |  |  |  | 38 | 35 | 41
Variable annuities | Maximum |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Death benefits paid in excess of the variable annuity account balances (are less than in 2016, 2017 and 2018) |  |  |  |  |  | 1 | 1 | 1
Property and casualty insurance | Other lines |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Special charges to increase asbestos and environmental reserves |  | $ 18 |  | $ 89 |  | 18 | 89 | 36
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement |  |  |  |  |  |  | $ 18 |
Special charges related to the exit of certain lines of business within subsidiaries |  |  |  |  |  |  |  | 65
Property and casualty insurance | Other lines | Increased insurance loss reserves related to medical malpractice and general liability lines |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Special charges related to the exit of certain lines of business within subsidiaries |  |  |  |  | $ 57 |  |  |
Neon Capital Limited | Property and casualty insurance |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement |  |  | 42 |  |  |  |  |
Neon Capital Limited | Property and casualty insurance | Other lines |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement |  |  | 18 |  |  |  |  |
Special charges related to the exit of certain lines of business within subsidiaries |  |  |  |  |  |  |  | $ 65
Neon Capital Limited | Property and casualty insurance | Other lines | Reinsurance to close agreement |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement |  |  | 18 |  |  |  |  |
Neon Capital Limited | Neon Capital Limited | Current lines |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement |  |  | $ 24 |  |  |  |  |
Great American Life Insurance Company | Life insurance |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |
Increased statutory surplus resulting from reinsurance treaty | $ 510 |  |  |  |  | $ 510 |  |

X
- Definition Aggregate guaranteed minimum death benefit value (assuming every variable annuity policyholder died on that date) on variable annuity policies in excess of the fair value of the underlying variable annuities. + References No definition available. + Details
Name: | afg_AggregateGuaranteedMinimumDeathBenefitValueOnVariableAnnuityPoliciesInForce
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of dividends that could be paid as of the balance sheet date without violating the most restrictive debt covenants. + References No definition available. + Details
Name: | afg_DividendPaymentsWithoutViolatingMostRestrictiveDebtCovenants
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Favorable prior year reserve development of the Company's liability for losses and loss adjustment expenses related to certain lines of business within subsidiaries including exited and ongoing lines of business in connection with a reinsurance to close agreement. + References No definition available. + Details
Name: | afg_FavorablePriorYearReserveDevelopmentRelatedToCertainLinesOfBusinessWithinSubsidiariesInConnectionWithAReinsuranceToCloseAgreement
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Basis spread on variable rate on advances from Federal Home Loan Bank. + References No definition available. + Details
Name: | afg_FederalHomeLoanBankAdvancesGeneralDebtObligationDisclosuresBasisSpreadonVariableRate
Namespace Prefix: | afg_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition The sum of the known and estimated amounts payable as of the balance sheet date to traditional long-term care insurance policyholders, net of reinsurance recoverables. + References No definition available. + Details
Name: | afg_LongTermCareInsuranceReserves
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The annual costs accrued for reinsurance coverage during the period. + References No definition available. + Details
Name: | afg_ReinsuranceCoverageAnnualCostForCatastropheBondStructure
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Restricted assets that are deposits with non-US regulatory authorities. + References No definition available. + Details
Name: | afg_RestrictedAssetsDepositsWithNonUnitedStatesRegulatoryAuthorities
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Special charges related to the exit of certain lines of business within subsidiaries. + References No definition available. + Details
Name: | afg_SpecialChargesRelatedToTheExitOfCertainLinesOfBusinessWithinSubsidiaries
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Special charges to increase asbestos and environmental reserves. + References No definition available. + Details
Name: | afg_SpecialChargesToIncreaseAsbestosAndEnvironmentalReserves
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Undrawn letters of credit, collateralized. + References No definition available. + Details
Name: | afg_UndrawnLettersOfCreditCollateralized
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of life insurance issued and outstanding ceded to other entity, as disclosed in supplementary reinsurance information. Includes, but is not limited to, dividend and adjustment to face value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Paragraph Column C -Subsection 17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17(Column C)) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915 + Details
Name: | srt_LifeInsuranceInForceCeded
Namespace Prefix: | srt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, before effect of reinsurance, of life insurance issued and outstanding, as disclosed in supplementary reinsurance information. Includes, but is not limited to, dividend and adjustment to face value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Paragraph Column B -Subsection 17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17(Column B)) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915 + Details
Name: | srt_LifeInsuranceInForceGross
Namespace Prefix: | srt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822 + Details
Name: | us-gaap_AdvancesFromFederalHomeLoanBanks
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 825 -Section 50 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=75763970&loc=SL75763979-209797 + Details
Name: | us-gaap_AssetsHeldByInsuranceRegulators
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of written premiums ceded to other entities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
Name: | us-gaap_CededPremiumsWritten
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentDescriptionOfVariableRateBasis
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of paid and unpaid common stock dividends declared with the form of settlement in cash. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 + Details
Name: | us-gaap_DividendsCommonStockCash
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of the collateral pledged in support of federal home loan bank advances outstanding. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822 + Details
Name: | us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of advances from Federal Home Loan Bank (FHLBank) maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822 + Details
Name: | us-gaap_FederalHomeLoanBankAdvancesMaturitiesSummaryDueFromOneToTwoYearsOfBalanceSheetDate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of advances from Federal Home Loan Bank (FHLBank) maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 + Details
Name: | us-gaap_FederalHomeLoanBankAdvancesMaturitiesSummaryDueFromTwoToThreeYearsOfBalanceSheetDate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of advances from Federal Home Loan Bank (FHLBank) maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 + Details
Name: | us-gaap_FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 325 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=75031641&loc=d3e63345-112809 + Details
Name: | us-gaap_FederalHomeLoanBankStock
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Interest expense incurred during the reporting period on long-term borrowings associated with Federal Home Loan Bank and Federal Reserve Bank advances. + References No definition available. + Details
Name: | us-gaap_InterestExpenseFederalHomeLoanBankAndFederalReserveBankAdvancesLongTerm
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
Name: | us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of cash outflow to policyholders and contract holders for guaranteed minimum benefit payments. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 17 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3367-108585 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 55 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=6588021&loc=d3e7104-158389 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 80 -Section 50 -Paragraph 1 -Subparagraph (d)(4) -URI http://asc.fasb.org/extlink&oid=6484115&loc=d3e19393-158473 + Details
Name: | us-gaap_LiabilitiesForGuaranteesOnLongDurationContractsPaymentForBenefits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of cash inflow from collection of advance by Federal Home Loan Bank (FHLBank), classified as investing activity. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585 + Details
Name: | us-gaap_ProceedsFromFederalHomeLoanBankAdvances
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of reduction of provision for policy benefits and costs incurred for policies ceded. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=99397103&loc=d3e6811-158387 + Details
Name: | us-gaap_ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Stated amount that is the upper retention limit per entity policy. + References No definition available. + Details
Name: | us-gaap_ReinsuranceRetentionPolicyAmountRetained
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of risk reinsured in excess of stated retention per company policy. + References No definition available. + Details
Name: | us-gaap_ReinsuranceRetentionPolicyExcessRetentionAmountReinsured
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Percentage of risk reinsured in excess of stated retention per entity policy. + References No definition available. + Details
Name: | us-gaap_ReinsuranceRetentionPolicyExcessRetentionPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of dividends that can be declared or paid without approval of regulatory agency. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(e)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
Name: | us-gaap_StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithoutRegulatoryApproval
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount of statutory capital and surplus (stockholders' equity) as of the balance sheet date using prescribed or permitted statutory accounting practices (rather than GAAP, if different) of the state or country. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(23)(c)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6486098&loc=d3e24708-158529 + Details
Name: | us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Current year monetary amount of the change in worker's compensation reserve liability resulting from the discount applied to reduce the reserve to present value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.(a),13(b)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
Name: | us-gaap_WorkersCompensationDiscountAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Percent discount applied to worker's compensation reserve liability to reduce the reserve to present value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=99382578&loc=d3e14754-158437 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.13(b)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6482852&loc=d3e14931-158439 + Details
Name: | us-gaap_WorkersCompensationDiscountPercent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | afg_InsuranceAxis=afg_FederalHomeLoanBanksAdvancesRefinancedTermsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=afg_CatastropheBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=us-gaap_LifeInsuranceSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=us-gaap_VariableAnnuityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=afg_PropertyAndCasualtyInsuranceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsegmentsAxis=afg_OtherLinesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=afg_IncreasedInsuranceLossReservesRelatedToMedicalMalpracticeAndGeneralLiabilityLinesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ConsolidatedEntitiesAxis=afg_NeonCapitalLimitedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=afg_ReinsuranceToCloseAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=afg_NeonCapitalLimitedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsegmentsAxis=afg_OngoingLinesOfBusinessMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=afg_GreatAmericanLifeInsuranceCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |