Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		$ 41	$ 176	$ 458	$ 500
Realized gains (losses) on securities		(12)	2	(1)	(32)
Realized gains on subsidiaries		0	0	0	2
Earnings before income taxes		29	178	457	470
Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		(81)	42	69	126
Investment and other income, net	[1]	87	79	271	269
Earnings before realized gains (losses) and income taxes		6	121	340	395
Annuity
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		102	107	283	236
Run-off Long-term Care and Life
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		2	1	4	0
Other
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	[2]	(69)	(53)	(169)	(131)
Specialty Property and transportation | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		6	44	70	91
Specialty casualty | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		2	13	46	65
Specialty financial | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		(3)	19	42	64
Other specialty | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		4	2	3	7
Other lines | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	[3]	$ (90)	$ (36)	$ (92)	$ (101)

[1] Includes pretax income of $13 million (before noncontrolling interest) from the sale of a hotel in the first quarter of 2017 and pretax income of $32 million (before noncontrolling interest) from the sale of an apartment property in the second quarter of 2016.

[2] Includes holding company interest and expenses, including losses on retirement of debt of $4 million in the third quarter of 2017 and $7 million in the second quarter of 2017, and special charges of $24 million and $5 million in the third quarter of 2017 and 2016, respectively, to increase A&E reserves related to AFG’s former railroad and manufacturing operations.

[3] Includes special charges of $89 million and $36 million in the third quarter of 2017 and 2016, respectively, to increase asbestos and environmental (“A&E”) reserves and a $65 million special charge related to the exit of certain lines of business with AFG’s Lloyd’s-based insurer, Neon, in the second quarter of 2016.