Additional Information - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Commitments to fund credit facilities and limited partnerships	$ 513
Retirement and employee savings plan expense	$ 63	$ 41	$ 61

Represents commitments to fund credit facilities and contribute capital to certain limited partnership investments at a future date.

No definition available.

Name:	afg_UnfundedCommitmentsToCreditFacilitiesAndLimitedPartnerships
Namespace Prefix:	afg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant