Condensed Financial Information of Parent Company (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Assets:
Cash and cash equivalents	$ 1,705		$ 1,324		$ 1,099	$ 1,120
Total assets	39,171		35,838		32,241
Liabilities and Equity [Abstract]
Long-term debt	953		934
Shareholders' equity	4,578		4,411
Total liabilities and equity	39,171		35,838
AFG [Member]
Assets:
Cash and cash equivalents	279		415		370	197
Investment in securities	44		39
Investment in subsidiaries	5,155	[1]	4,732	[1]
Other investments	2		2
Other assets	117		105
Total assets	5,597		5,293
Liabilities and Equity [Abstract]
Long-term debt	840		600
Other liabilities	179		282
Shareholders' equity	4,578		4,411
Total liabilities and equity	$ 5,597		$ 5,293

[1] Investment in subsidiaries includes intercompany receivables and payables.