Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	$ 119	$ 195	$ 296	$ 627
Realized gains (losses) on securities	45	(18)	(302)	222
Realized losses on subsidiaries	(30)	0	(30)	0
Earnings (loss) before income taxes	134	177	(36)	849
Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	18	54	114	200
Investment and other income, net	100	118	249	328
Earnings before realized gains (losses) and income taxes	118	172	363	528
Annuity
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	78	73	90	234
Other
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	(77)	(50)	(157)	(135)
Specialty Property and transportation \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	47	38	107	81
Specialty casualty \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	53	23	132	106
Specialty financial \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	13	26	30	60
Other specialty \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	(9)	1	(22)	(11)
Other lines \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	$ (86)	$ (34)	$ (133)	$ (36)

Net investment income plus other income less other expenses.

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