Segments of Operations (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended						3 Months Ended	12 Months Ended			3 Months Ended
	Dec. 31, 2012	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Jun. 30, 2011 Other [Member]	Dec. 31, 2012 Other [Member]	Dec. 31, 2011 Other [Member]	Dec. 31, 2010 Other [Member]	Sep. 30, 2012 Other Lines [Member]	Jun. 30, 2011 Other Lines [Member]
Segments of Operations (Textual) [Abstract]
Revenue derived from sales of property and casualty insurance outside of the United States		5.00%		5.00%		4.00%
Special charges to increase asbestos and environmental reserves								$ 9				$ 31	$ 50
Loss recognition charge on closed block of long-term care insurance	153
Earnings (losses) of managed investment entities attributable to noncontrolling interests		(98)	[1]	(24)	[1]	(64)	[1]		(98)	(24)	(64)
Loss on retirement of debt									8
Charge for a labor matter related to former operations									$ 15

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