XML 129 R107.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Additional Information - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract] |  |  |
Commitments to fund credit facilities and limited partnerships | $ 499 |  |
Retirement and employee savings plan expense | $ 61 | $ 41 | $ 39

X
- Definition Represents commitments to fund credit facilities and contribute capital to certain limited partnership investments at a future date. + References No definition available. + Details
Name: | afg_UnfundedCommitmentsToCreditFacilitiesAndLimitedPartnerships
Namespace Prefix: | afg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of cost (reversal of cost) for other postretirement benefits. Excludes pension benefits. + References No definition available. + Details
Name: | us-gaap_OtherPostretirementBenefitExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration