Segments of Operations (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012 Property and Casualty Insurance [Member]	Jun. 30, 2011 Property and Casualty Insurance [Member]	Sep. 30, 2012 Other Segment [Member]	Sep. 30, 2011 Other Segment [Member]	Sep. 30, 2012 Other Segment [Member]	Sep. 30, 2011 Other Segment [Member]	Sep. 30, 2012 Medicare supplement and critical illness operations [Member]	Sep. 30, 2011 Medicare supplement and critical illness operations [Member]	Sep. 30, 2012 Medicare supplement and critical illness operations [Member]	Sep. 30, 2011 Medicare supplement and critical illness operations [Member]
Segments of Operations (Textual) [Abstract]
Special charges to increase asbestos and environmental reserves									$ 31	$ 50
Earnings from Medicare supplement and critical illness operations															10	11	28	21
Earnings (losses) of managed investment entities attributable to noncontrolling interests	(18)	[1]	8	[1]	(64)	[1]	(47)	[1]			(18)	8	(64)	(47)
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.