Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Segment Reporting Information
Earned premiums	$ 1,918	$ 1,693
Fee revenues	4	4
Total revenues	2,241	1,218
Investment income, net of expenses	210	185
Investment gains and losses, net	106	(666)
Other revenues	3	2
Income before Income Taxes	268	(351)
Assets	30,474		$ 29,732
Consolidated Property And Casualty Insurance
Segment Reporting Information
Earned premiums	1,841	1,618
Assets	5,229		5,178
Life Insurance Segment
Segment Reporting Information
Assets	1,529		1,518
Investment Segment
Segment Reporting Information
Assets	22,805		22,133
Corporate and Other
Segment Reporting Information
Assets	911		$ 903
Operating Segments | Commercial Insurance
Segment Reporting Information
Earned premiums	1,056	962
Fee revenues	1	1
Total revenues	1,057	963
Income Before Income Taxes	(2)	76
Operating Segments | Commercial Insurance | Commercial Casualty Line
Segment Reporting Information
Earned premiums	377	336
Operating Segments | Commercial Insurance | Commercial Property Line
Segment Reporting Information
Earned premiums	299	274
Operating Segments | Commercial Insurance | Commercial Auto Line
Segment Reporting Information
Earned premiums	213	205
Operating Segments | Commercial Insurance | Workers' Compensation Line
Segment Reporting Information
Earned premiums	74	67
Operating Segments | Commercial Insurance | Other Commercial Lines
Segment Reporting Information
Earned premiums	93	80
Operating Segments | Personal Insurance
Segment Reporting Information
Earned premiums	464	402
Fee revenues	1	1
Total revenues	465	403
Income Before Income Taxes	(57)	65
Operating Segments | Personal Insurance | Personal Auto
Segment Reporting Information
Earned premiums	166	152
Operating Segments | Personal Insurance | Home Owner Line
Segment Reporting Information
Earned premiums	232	195
Operating Segments | Personal Insurance | Other Personal Lines
Segment Reporting Information
Earned premiums	66	55
Operating Segments | Excess and Surplus Lines Insurance
Segment Reporting Information
Earned premiums	127	112
Fee revenues	0	1
Total revenues	127	113
Income Before Income Taxes	13	16
Operating Segments | Life Insurance Segment
Segment Reporting Information
Earned premiums	77	75
Fee revenues	2	1
Total revenues	79	76
Income Before Income Taxes	8	7
Operating Segments | Investment Segment
Segment Reporting Information
Total revenues	316	(481)
Investment income, net of expenses	210	185
Investment gains and losses, net	106	(666)
Income Before Income Taxes	286	(508)
Corporate, Non-Segment
Segment Reporting Information
Total revenues	197	144
Corporate, Non-Segment | Reinsurance assumed and other non segment
Segment Reporting Information
Earned premiums	194	142
Corporate, Non-Segment | Corporate and Other
Segment Reporting Information
Other revenues	3	2
Income Before Income Taxes	$ 20	$ (7)