Condensed Financial Information of Parent Company (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Assets:
Cash and investments	$ 25,577	$ 22,670
Investment in subsidiaries	0	0
Other assets	2,386	2,082
Total assets	36,042	32,454	27,683
Liabilities and Equity:
Long-term debt	934	952
Other liabilities	2,479	2,057
Shareholders' equity	4,545	4,470
Total liabilities and equity	36,042	32,454
AFG [Member]
Assets:
Cash and investments	456	412
Investment in subsidiaries	4,866	4,816
Other assets	105	36
Total assets	5,427	5,264
Liabilities and Equity:
Long-term debt	600	600
Other liabilities	282	194
Shareholders' equity	4,545	4,470
Total liabilities and equity	$ 5,427	$ 5,264