Derivatives (Details) (Not Designated as Hedging Instrument [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	$ 467	$ 433
Derivative liability, at fair value	916	814
MBS with embedded derivatives [Member] | Fixed maturities [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	162	140
Public company warrants [Member] | Equity securities [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	17	19
Interest rate swaptions [Member] | Other investments [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	1	2
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	904	804
Equity index call options [Member] | Other investments [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	287	272
Reinsurance contracts (embedded derivative) [Member] | Other liabilities [Member]
Derivatives included in AFG' s Balance Sheet at fair value
Derivative liability, at fair value	$ 12	$ 10