Segments of Operations (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Operating earnings before income taxes by significant business segment and sub-segment
Realized gains (losses) on securities	$ 85		$ 8		$ 145		$ 27
Realized gains (losses) on subsidiaries	156				155		(3)
Operating earnings before income taxes	285		156		567		318
Property and Casualty Insurance [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)	(16)		58		77		92
Investment and other income, net	58		65		174		205
Realized gains	44		15		88		47
Operating earnings before income taxes	86		138		339		344
Annuity and Supplemental Insurance [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Operations	81	[1]	47	[1]	224	[1]	157	[1]
Realized gains (losses) on securities	41		(8)		57		(22)
Realized gains (losses) on subsidiaries	156				155		(2)
Operating earnings before income taxes	278		39		436		133
Other Segment [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Operating earnings before income taxes	(79)	[2]	(21)	[2]	(208)	[2]	(159)	[2]
Specialty Property and transportation [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)			5		33		38
Specialty casualty [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)	8		20		45		38
Specialty financial [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)	1		24		28		52
Specialty Other [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)	7		9		10		14
Other Lines [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)	$ (32)	[3]		[3]	$ (39)	[3]	$ (50)	[3]

[1] Includes earnings from the Medicare supplement and critical illness operations, which were sold in August 2012, of $10 million and $11 million for the third quarter and $28 million and $21 million for the first nine months of 2012 and 2011, respectively.

[2] Includes holding company expenses and earnings (losses) of managed investment entities attributable to noncontrolling interests of ($18) million and $8 million for the third quarter and ($64) million and ($47) million for the first nine months of 2012 and 2011, respectively. Holding company expenses for the third quarter of 2012 include an $8 million loss on retirement of debt and a $15 million charge for a labor matter related to AFG’s former railroad operations.

[3] Includes third quarter 2012 and second quarter 2011 special charges of $31 million and $50 million, respectively, to increase asbestos and environmental reserves.