Derivatives (Details) (Not Designated as Hedging Instrument [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	$ 480	$ 499
Derivative liability, at fair value	1,256	1,173
MBS with embedded derivatives [Member] \| Fixed maturities [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	164	158
Public company warrants [Member] \| Equity securities [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	0	19
Interest rate swaptions [Member] \| Other investments [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	0	0
Fixed-indexed annuities (embedded derivative) [Member] \| Annuity benefits accumulated [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative liability, at fair value	1,243	1,160
Equity index call options [Member] \| Other investments [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	316	322
Reinsurance contracts (embedded derivative) [Member] \| Other liabilities [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative liability, at fair value	$ 13	$ 13

Fair value, after offset of derivative liability, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, after offset of derivative asset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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