Fair Value Measurements (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Professional	Jun. 30, 2012	Dec. 31, 2012
Fair Value Measurements (Textual) [Abstract]
AFG's internal investment professionals			20
Level 3 assets as a percentage of total assets measured at fair value			3.00%
Percentage of level 3 assets that were priced using non-binding broker quotes			82.00%
Percentage of internally developed Level 3 assets to total assets			1.00%
Percentage of internally developed Level 3 assets to Shareholders' equity			3.00%
Fair value of derivatives in annuity benefits accumulated measured using a discounted cash flow approach	$ 577		$ 577		$ 465
Total realized/unrealized losses included in net income on liabilities still outstanding	9	14	24	51
Preferred Stock [Member]
Fair Value Measurements (Textual) [Abstract]
Number of preferred stocks transferred from Level 2 to Level 1	5		5
Fair value of assets transferred from Level 2 to Level 1	11		11
Number of preferred stocks transferred from Level 1 to Level 2		6		6
Fair value of assets transferred from Level 1 to Level 2		$ 35		$ 35
Embedded Derivative Financial Instruments, Majority of Future Years [Member] | Minimum [Member]
Fair Value Measurements (Textual) [Abstract]
Unobservable input surrenders used in Level 3 fair value determination			5.00%
Embedded Derivative Financial Instruments, Majority of Future Years [Member] | Maximum [Member]
Fair Value Measurements (Textual) [Abstract]
Unobservable input surrenders used in Level 3 fair value determination			12.00%
Embedded Derivative Financial Instruments [Member] | Minimum [Member]
Fair Value Measurements (Textual) [Abstract]
Unobservable input surrenders used in Level 3 fair value determination			4.00%
Embedded Derivative Financial Instruments [Member] | Maximum [Member]
Fair Value Measurements (Textual) [Abstract]
Unobservable input surrenders used in Level 3 fair value determination			20.00%