Managed Investment Entities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Gains (losses) on change in fair value of assets/liabilities (a):
Assets	$ (2)	$ (12)	$ 53	$ 17
Liabilities	(19)	(10)	(103)	(72)
Management fees paid to AFG	4	5	8	8
Collateralized loan obligations' earnings (losses) attributable to:
AFG shareholders	5	1	10	7
Noncontrolling interests	$ (18)	$ (20)	$ (46)	$ (55)