Condensed Consolidating Information (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Revenues:
Property and casualty insurance premiums	$ 603	$ 599
Life, accident and health premiums	105	110
Realized gains (losses)	44	(3)
Income of managed investment entities		(8)
Investment and other income	361	341
Total revenues	1,113	1,039
Costs and Expenses:
Insurance benefits and expenses	824	806
Interest charges on borrowed money	21	21
Expenses of managed investment entities	19	18
Other operating and general expenses	103	92
Total costs and expenses	967	937
Operating earnings before income taxes	146	102
Provision (credit) for income taxes	58	48
Net earnings, including noncontrolling interests	88	54
Less: Net earnings (loss) attributable to noncontrolling interests	(25)	(34)
Net earnings attributable to shareholders	113	88
AFG [Member]
Revenues:
Investment and other income	2	2
Equity in earnings of subsidiaries	203	167
Total revenues	205	169
Costs and Expenses:
Interest charges on borrowed money	16	16
Other operating and general expenses	18	17
Total costs and expenses	34	33
Operating earnings before income taxes	171	136
Provision (credit) for income taxes	58	48
Net earnings, including noncontrolling interests	113	88
Net earnings attributable to shareholders	113	88
GAFRI [Member]
Revenues:
Investment and other income	2	3
Equity in earnings of subsidiaries	78	47
Total revenues	80	50
Costs and Expenses:
Other operating and general expenses	4	3
Total costs and expenses	4	3
Operating earnings before income taxes	76	47
Provision (credit) for income taxes	27	17
Net earnings, including noncontrolling interests	49	30
Net earnings attributable to shareholders	49	30
AAG Holding [Member]
Revenues:
Equity in earnings of subsidiaries	84	55
Total revenues	84	55
Costs and Expenses:
Interest charges on borrowed money	6	6
Other operating and general expenses	2	1
Total costs and expenses	8	7
Operating earnings before income taxes	76	48
Provision (credit) for income taxes	27	17
Net earnings, including noncontrolling interests	49	31
Net earnings attributable to shareholders	49	31
All Other Subs [Member]
Revenues:
Property and casualty insurance premiums	603	599
Life, accident and health premiums	105	110
Realized gains (losses)	45	(3)
Income of managed investment entities		(8)
Investment and other income	362	343
Total revenues	1,115	1,041
Costs and Expenses:
Insurance benefits and expenses	824	806
Interest charges on borrowed money	4	4
Expenses of managed investment entities	19	18
Other operating and general expenses	80	72
Total costs and expenses	927	900
Operating earnings before income taxes	188	141
Provision (credit) for income taxes	72	60
Net earnings, including noncontrolling interests	116	81
Less: Net earnings (loss) attributable to noncontrolling interests	(25)	(34)
Net earnings attributable to shareholders	141	115
Consol. Entries [Member]
Revenues:
Realized gains (losses)	(1)
Investment and other income	(5)	(7)
Equity in earnings of subsidiaries	(365)	(269)
Total revenues	(371)	(276)
Costs and Expenses:
Interest charges on borrowed money	(5)	(5)
Other operating and general expenses	(1)	(1)
Total costs and expenses	(6)	(6)
Operating earnings before income taxes	(365)	(270)
Provision (credit) for income taxes	(126)	(94)
Net earnings, including noncontrolling interests	(239)	(176)
Net earnings attributable to shareholders	$ (239)	$ (176)