Derivatives (Details) (Not Designated as Hedging Instrument [Member], USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	$ 206	$ 199
Derivative liability, at fair value	317	204
MBS with embedded derivatives [Member] | Fixed Maturities [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	93	101
Interest rate swaptions [Member] | Other Investments [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	21	21
Indexed annuities embedded derivative [Member] | Annuity benefits accumulated [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative liability, at fair value	299	190
Equity index call options [Member] | Other Investments [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	92	77
Reinsurance contracts embedded derivative [Member] | Other Liabilities [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative liability, at fair value	$ 18	$ 14