Derivatives (Details) (Not Designated as Hedging Instrument [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	$ 433	$ 243
Derivative liability, at fair value	814	482
MBS with embedded derivatives [Member] | Fixed maturities [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	140	110
Public company warrants [Member] | Equity securities [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	19	0
Interest rate swaptions [Member] | Other investments [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	2	1
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	804	465
Equity index call options [Member] | Other investments [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	272	132
Reinsurance contracts (embedded derivative) [Member] | Other liabilities [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative liability, at fair value	$ 10	$ 17