Segments of Operations (Details Textuals) (USD $) In Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segments of Operations (Textuals) [Abstract]
Earnings (losses) of managed investment entities attributable to noncontrolling interests	$ 8		$ (4)	$ (47)	$ (37)
Other Lines [Member]
Segments of Operations (Textuals) [Abstract]
Special charges to increase asbestos and environmental reserves		50		50
Other Segment [Member]
Segments of Operations (Textuals) [Abstract]
Earnings (losses) of managed investment entities attributable to AFG shareholders, including management fees	3		8	18	23
Earnings (losses) of managed investment entities attributable to noncontrolling interests	8		(4)	(47)	(37)
Special charges to increase asbestos and environmental reserves		$ 9		$ 9