Insurance (Details Textual) (USD $)	3 Months Ended		12 Months Ended				12 Months Ended			3 Months Ended			0 Months Ended		12 Months Ended			3 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Minimum [Member]	Dec. 31, 2013 Minimum [Member] LIBOR [Member]	Dec. 31, 2013 Maximum [Member] LIBOR [Member]	Dec. 31, 2013 Average [Member] LIBOR [Member]	Sep. 30, 2013 Property and Casualty Insurance [Member]	Sep. 30, 2012 Property and Casualty Insurance [Member]	Jun. 30, 2011 Property and Casualty Insurance [Member]	Dec. 31, 2013 Life insurance [Member]	Dec. 31, 2012 Life insurance [Member]	Dec. 31, 2013 Life insurance [Member]	Dec. 31, 2012 Life insurance [Member]	Dec. 31, 2011 Life insurance [Member]	Dec. 31, 2012 Run-off Long-term Care and Life [Member]	Dec. 31, 2013 Run-off Long-term Care and Life [Member]
Insurance [Line Items]
Carrying value of securities owned by U.S.-based insurance subsidiaries on deposit			$ 1,100,000,000
Undrawn letters of credit			189,000,000
Undrawn letters of credit, collateralized			16,000,000
Workers' compensation insurance discount rate			4.50%	4.50%
Workers' compensation insurance discount, which has reduced the liability for unpaid losses and loss adjustment expenses			20,000,000	22,000,000
Special charges to increase asbestos and environmental reserves										54,000,000	31,000,000	50,000,000
Pretax charge on closed block of long-term care insurance																		153,000,000	0
Long-term care insurance reserves, net of reinsurance recoverables			726,000,000
Investment in Federal Home Loan Bank capital stock			34,000,000
Proceeds received under funding agreements with the Federal Home Loan Bank	200,000,000	240,000,000
Advances from Federal Home Loan Bank			440,000,000
FHLB advances, basis spread on variable rate							0.02%	0.23%	0.32%
Description of variable rate basis			LIBOR
Estimated fair value of commercial mortgage-backed securities held as collateral by the Federal Home Loan Bank			565,000,000
Interest on advances from Federal Home Loan Bank (are less than in 2011 and 2012)			1,000,000	1,000,000	1,000,000
Maximum amount of dividends available to be paid by insurance subsidiaries to AFG without prior approval of regulatory authorities			610,000,000
Dividends on Common Stock			(161,000,000)	(91,000,000)	(69,000,000)
Dividends payments without violating the most restrictive debt covenants, minimum						1,000,000,000
Life insurance in force, ceded premiums													13,430,000,000	14,540,000,000
Life insurance in force, direct premiums													17,980,000,000	19,440,000,000
Life written premiums ceded															44,000,000	42,000,000	44,000,000
Aggregate guaranteed minimum death benefit value on variable annuity polices in force			26,000,000	40,000,000
Death benefits paid in excess of the variable annuity account balances (are less than in 2011, 2012 and 2013)			$ 1,000,000	$ 1,000,000	$ 1,000,000