Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	$ 284	$ 47	$ 783	$ 222
Realized gains (losses) on securities	(17)	23	103	(197)
Realized gains (losses) on subsidiaries	0	(30)	4	(30)
Earnings (loss) from continuing operations before income taxes	267	40	890	(5)
Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	168	18	454	114
Investment and other income, net	161	100	451	249
Earnings before realized gains (losses) and income taxes	329	118	905	363
Other
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	(45)	(74)	(173)	(152)
Other \| Continuing operations \| Real estate-related investments
Segment Reporting Information [Line Items]
Earnings from real-estate related investments, net of DAC	0	3	51	11
Specialty Property and transportation \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	45	47	163	107
Specialty casualty \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	110	53	237	132
Specialty financial \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	26	13	72	30
Other specialty \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	(12)	(9)	(16)	(22)
Other lines \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	$ (1)	$ (86)	$ (2)	$ (133)

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Underwriting income (loss) for the property and casualty insurance segment, which is calculated as premiums earned less losses and loss adjustment expenses less commissions and other underwriting expenses.

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Amount of gain (loss) on sale or disposal of equity in securities of subsidiaries.

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