Contingencies	12 Months Ended
Contingencies	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies Establishing property and casualty insurance reserves for claims related to environmental exposures, asbestos and other mass tort claims is subject to uncertainties that are significantly greater than those presented by other types of claims. For this group of claims, traditional actuarial techniques that rely on historical loss development trends cannot be used and a range of reasonably possible losses cannot be estimated. In addition, accruals (included in other liabilities) have been recorded for various environmental and occupational injury and disease claims and other contingencies arising out of the railroad operations disposed of by American Premier’s predecessor, Penn Central Transportation Company (“PCTC”) and its subsidiaries, prior to its bankruptcy reorganization in 1978 and certain manufacturing operations disposed of by American Premier and Great American Financial Resources, Inc. (“GAFRI”). AFG completed an in-depth internal review of its asbestos and environmental (“A&E”) exposures in the third quarter of 2019. The review resulted in special A&E charges of $18 million for the property and casualty group and $11 million for the former railroad and manufacturing operations. AFG also completed an in-depth internal review of its A&E exposures in the third quarter of 2018, which resulted in special A&E charges of $18 million for the property and casualty group and $9 million for the former railroad and manufacturing operations. AFG completed a comprehensive external study of its A&E exposures in the third quarter of 2017 with the aid of specialty actuarial, engineering and consulting firms and outside counsel. The study resulted in special A&E charges of $89 million for the property and casualty group and $24 million for the former railroad and manufacturing operations. The property and casualty group’s liability for A&E reserves was $529 million at December 31, 2019; related recoverables from reinsurers (net of allowances for doubtful accounts) at that date were $146 million. At December 31, 2019, American Premier and its subsidiaries had liabilities for environmental and personal injury claims and other contingencies aggregating $84 million. The environmental claims consist of a number of proceedings and claims seeking to impose responsibility for hazardous waste remediation costs related to certain sites formerly owned or operated by the railroad and manufacturing operations. Remediation costs are difficult to estimate for a number of reasons, including the number and financial resources of other potentially responsible parties, the range of costs for remediation alternatives, changing technology and the time period over which these matters develop. The personal injury claims and other contingencies include pending and expected claims, primarily by former employees of PCTC, for injury or disease allegedly caused by exposure to excessive noise, asbestos or other substances in the workplace and other labor disputes. At December 31, 2019, GAFRI had a liability of $8 million for environmental costs and certain other matters associated with the sales of its former manufacturing operations. In December 2015, AFG completed the sale of substantially all of its run-off long-term care insurance business to HC2 Holdings, Inc. (“HC2”). In connection with obtaining regulatory approval for the transaction, AFG agreed to provide up to an aggregate of $35 million of capital support for the insurance companies, on an as-needed basis to maintain specified surplus levels, subject to immediate reimbursement by HC2 through a five-year capital maintenance agreement expiring in 2020. While management believes AFG has recorded adequate reserves for the items discussed above, the outcome is uncertain and could result in liabilities that may vary from amounts AFG has currently recorded. Such amounts could have a material effect on AFG’s future results of operations and financial condition. In addition, AFG and its subsidiaries are involved in litigation from time to time, generally arising in the ordinary course of business. This litigation may include, but is not limited to, general commercial disputes, lawsuits brought by policyholders, employment matters, reinsurance collection matters and actions challenging certain business practices of insurance subsidiaries. None of these matters are expected to have a material adverse impact on AFG’s results of operations or financial condition.