Condensed Financial Information of Parent Company (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statement of Other Comprehensive Income [Abstract]
Net earnings attributable to shareholders	$ 50	$ 226	$ 99	$ 113	$ 109	$ 97	$ 48	$ 88	$ 488	$ 342	$ 482
Other comprehensive income, net of tax									252	85	336
Comprehensive income attributable to shareholders									740	427	818
AFG [Member]
Statement of Other Comprehensive Income [Abstract]
Net earnings attributable to shareholders									488	342	482
Other comprehensive income, net of tax									252	85	336
Comprehensive income attributable to shareholders									$ 740	$ 427	$ 818