Managed Investment Entities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Gains (losses) on change in fair value of assets/liabilities (a):
Assets	$ 39	[1]	$ (88)	[1]	$ 92	[1]	$ (71)	[1]
Liabilities	(52)	[1]	89	[1]	(155)	[1]	17	[1]
Management fees paid to AFG	6		5		14		13
Collateralized loan obligations' earnings (losses) attributable to:
AFG shareholders	11	[2]	(2)	[2]	21	[2]	5	[2]
Noncontrolling interests	$ (18)	[2]	$ 8	[2]	$ (64)	[2]	$ (47)	[2]

[1] Included in Revenues in AFG’s Statement of Earnings.

[2] Included in Operating earnings before income taxes in AFG’s Statement of Earnings.