Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		$ 766	$ 745	$ 574
Realized gains (losses) on securities		19	(19)	52
Realized gains (losses) on subsidiaries		2	(161)	0
Earnings before income taxes		787	565	626
Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		236	225	212
Investment and other income, net	[1]	341	351	244
Earnings before realized gains (losses) and income taxes		577	576	456
Annuity
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		368	331	328
Run-off long-term care and life
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	[2]	2	14	(10)
Other
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	[3]	(181)	(176)	(200)
Property and transportation
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		166	48	21
Specialty casualty
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		78	146	136
Specialty financial
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		84	87	64
Other specialty
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		9	14	16
Other lines
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	[4]	$ (101)	$ (70)	$ (25)

[1] 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.

[2] AFG sold substantially all of its run-off long-term care insurance business in December 2015.

[3] Primarily holding company interest and expenses, including a $4 million loss on retirement of debt in the third quarter of 2015, and special charges to increase A&E reserves related to AFG’s former railroad and manufacturing operations ($5 million in 2016, $12 million in 2015 and $6 million in 2014) and losses of managed investment entities attributable to noncontrolling interests ($51 million in 2014). Following the adoption of new guidance in the first quarter of 2015, there are no longer earnings (losses) of managed investment entities that are attributable to noncontrolling interests. See Note A — “Accounting Policies — Managed Investment Entities.”

[4] Includes a special charge of $65 million related to the exit of certain lines of business within AFG’s Lloyd’s-based insurer, Neon, in the second quarter of 2016 and special charges to increase asbestos and environmental (“A&E”) reserves of $36 million, $67 million and $24 million in 2016, 2015 and 2014, respectively.