Segments of Operations - Revenues by segment and sub-segment (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2020		Jun. 30, 2019	Jun. 30, 2020		Jun. 30, 2019
Segment Reporting Information [Line Items]
Total premiums earned		$ 1,184		$ 1,200	$ 2,393		$ 2,373
Net investment income		468	[1]	580	1,012	[1]	1,122
Other income		51		56	108		112
Revenues before realized gains (losses)		1,747		1,904	3,573		3,744
Realized gains (losses) on securities		204		56	(347)		240
Total revenues		1,951		1,960	3,226		3,984
Property and Casualty Insurance
Segment Reporting Information [Line Items]
Total premiums earned		1,184		1,200	2,393		2,373
Net investment income		72	[2]	124	165	[2]	228
Other income		3		2	8		5
Revenues before realized gains (losses)		1,259		1,326	2,566		2,606
Annuity
Segment Reporting Information [Line Items]
Net investment income		384		451	806		886
Other income		30		30	65		58
Revenues before realized gains (losses)		414		481	871		944
Other
Segment Reporting Information [Line Items]
Revenues before realized gains (losses)		74		97	136		194
Specialty Property and transportation | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Total premiums earned		390		379	776		740
Specialty casualty | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Total premiums earned		547		634	1,103		1,263
Specialty financial | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Total premiums earned		144		151	300		297
Other specialty | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Total premiums earned		42		36	82		73
Other lines | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Total premiums earned	[3]	$ 61		$ 0	$ 132		$ 0

[1] Net investment income in the second quarter and first six months of 2020 includes income of less than $1 million and losses of $6 million, respectively, on investments held by the companies that comprise the Neon exited lines due primarily to the $7 million loss in first quarter of 2020 recorded on equity securities that are carried at fair value through net investment income.

[2] Includes income of less than $1 million for the second quarter of 2020 and a loss of $6 million in the Neon exited lines in the first six months of 2020 (primarily from the change in fair value of equity securities).

[3] Represents premiums earned in the Neon exited lines during the second quarter and first six months of 2020. Neon’s $89 million and $177 million in earned premiums during the second quarter and first six months of 2019, respectively, are included in the Specialty casualty sub-segment.