Insurance (Details Textual) (USD $)	3 Months Ended	12 Months Ended								3 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 GALIC [Member]	Dec. 31, 2011 GALIC [Member]	Dec. 31, 2012 GALIC [Member] Minimum [Member] LIBOR [Member]	Dec. 31, 2012 GALIC [Member] Maximum [Member] LIBOR [Member]	Dec. 31, 2012 GALIC [Member] Average [Member] LIBOR [Member]	Sep. 30, 2012 Property and Casualty Insurance [Member]	Jun. 30, 2011 Property and Casualty Insurance [Member]
Insurance [Line Items]
Special charge to increase asbestos and environmental reserves										$ 31,000,000	$ 50,000,000
Pretax charge on closed block of long-term care insurance	153,000,000
Long-term care insurance reserves, net of reinsurance recoverables	755,000,000	755,000,000
Investment in Federal Home Loan Bank capital stock					26,000,000
Proceeds received under funding agreements with the Federal Home Loan Bank					240,000,000	240,000,000
Maturity period on advances from Federal Home Loan Bank, earliest					5 years
Maturity period on advances from Federal Home Loan Bank, latest					7 years
Description of variable rate basis		LIBOR
FHLB advances, basis spread on variable rate							0.02%	0.03%	0.23%
Estimated fair value of commercial mortgage-backed securities held as collateral by the Federal Home Loan Bank					316,000,000
Interest on advances from Federal Home Loan Bank					1,000,000	1,000,000
Insurance (Textual) [Abstract]
Carrying value of securities owned by U.S.-based insurance subsidiaries on deposit	1,100,000,000	1,100,000,000
Undrawn letters of credit	198,000,000	198,000,000
Undrawn letters of credit, collateralized	16,000,000	16,000,000
Workers' compensation insurance discount rate		4.50%
Workers' compensation insurance discount, which has reduced the liability for unpaid losses and loss adjustment expenses	22,000,000	22,000,000
Face amount of life insurance, reinsured by AFG	14,000,000,000	14,000,000,000	16,000,000,000
Life written premiums ceded		42,000,000	44,000,000	49,000,000
Aggregate guaranteed minimum death benefit value on variable annuity polices in force	40,000,000	40,000,000	63,000,000
Death benefits paid in excess of the variable annuity account balances, maximum		$ 1,000,000	$ 1,000,000	$ 1,000,000