Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		$ 197	$ 150	$ 417	$ 324
Realized gains (losses) on securities		8	(16)	11	(34)
Realized gains on subsidiaries		0	2	0	2
Earnings before income taxes		205	136	428	292
Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		72	(3)	150	84
Investment and other income, net	[1]	91	115	184	190
Earnings before realized gains (losses) and income taxes		163	112	334	274
Annuity
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		85	76	181	129
Run-off Long-term Care and Life
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		2	0	2	(1)
Other
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	[2]	(53)	(38)	(100)	(78)
Specialty Property and transportation | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		21	15	64	47
Specialty casualty | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		29	23	44	52
Specialty financial | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		23	22	45	45
Other specialty | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		0	3	(1)	5
Other lines | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	[3]	$ (1)	$ (66)	$ (2)	$ (65)

[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 a $7 million loss on retirement of debt in the second quarter of 2017.

[3] Includes 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.