Segments of Operations - Narrative (Details) $ in Millions		3 Months Ended					12 Months Ended
		Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2016 USD ($) segment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of segments | segment							4
Revenue derived from sales of property and casualty insurance outside of the United States							4.00%	4.00%	5.00%
Other income							$ 224	$ 243	$ 122
Earnings (losses) of managed investment entities attributable to noncontrolling interests	[1]						0	0	(51)
Property and casualty insurance
Segment Reporting Information [Line Items]
Other income	[2]						51	78	9
Property and casualty insurance | Real estate investment
Segment Reporting Information [Line Items]
Other income			$ 32	$ 15		$ 51
Property and casualty insurance | Other lines
Segment Reporting Information [Line Items]
Special charges related to the exit of certain lines of business within subsidiaries			$ 65
Special charges to increase asbestos and environmental reserves		$ 36			$ 67		36	67	24
Other
Segment Reporting Information [Line Items]
Special charges to increase asbestos and environmental reserves							$ 5	$ 12	6
Write off of deferred debt issuance cost due to the retirement of debt					$ 4
Earnings (losses) of managed investment entities attributable to noncontrolling interests									$ (51)

[1] Included in earnings before income taxes in AFG’s Statement of Earnings.

[2] Includes pretax income of $32 million (before noncontrolling interest) from the sale of an apartment property in the second quarter of 2016, $51 million (before noncontrolling interest) from the sale of a hotel in the second quarter of 2015 and $15 million from the sale of an apartment property in the fourth quarter of 2015.