Condensed Financial Information of Parent Company (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues:
Investment and other income									$ 1,416	$ 1,385	$ 1,426
Total revenues	1,283	1,335	1,093	1,039	1,156	1,255	1,052	1,034	4,750	4,497	4,320
Costs and Expenses:
Other operating and general expenses									363	378	463
Total costs and expenses									4,190	3,808	3,508
Operating earnings before income taxes									560	689	812
Provision for income taxes									240	266	282
Net Earnings Attributable to Shareholders	109	96	55	83	133	132	108	106	343	479	519
AFG [Member]
Revenues:
Dividends from subsidiaries									544	554	673
Equity in undistributed earnings of subsidiaries									166	296	223
Investment and other income									2	4	2
Total revenues									712	854	898
Costs and Expenses:
Interest charges on intercompany borrowings									11	12	13
Interest charges on other borrowings									53	46	37
Other operating and general expenses									65	51	47
Total costs and expenses									129	109	97
Operating earnings before income taxes									583	745	801
Provision for income taxes									240	266	282
Net Earnings Attributable to Shareholders									$ 343	$ 479	$ 519