Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-17, Insurance Companies, Reinsurance
Gross amounts, life insurance in force	$ 122,053	$ 120,147	$ 116,697
Gross amounts	7,801	7,056	6,366
Ceded amounts to other companies, life insurance in force	39,692	39,665	39,204
Ceded premiums earned	412	392	331
Assumed amounts from other companies, life insurance in force	0	0	0
Assumed amounts from other companies	569	561	443
Net amounts, life insurance in force	82,361	80,482	77,493
Premiums Earned, Net	$ 7,958	$ 7,225	$ 6,478
Percentage of amounts assumed to net, life insurance in force	0.00%	0.00%	0.00%
Percentage of amounts assumed to net	7.20%	7.80%	6.80%
Commercial Insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance
Gross amounts	$ 4,399	$ 4,150	$ 3,777
Ceded premiums earned	147	137	115
Assumed amounts from other companies	12	11	12
Premiums Earned, Net	$ 4,264	$ 4,024	$ 3,674
Percentage of amounts assumed to net	0.30%	0.30%	0.30%
Personal Insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance
Gross amounts	$ 2,117	$ 1,755	$ 1,586
Ceded premiums earned	74	67	45
Assumed amounts from other companies	1	1	1
Premiums Earned, Net	$ 2,044	$ 1,689	$ 1,542
Percentage of amounts assumed to net	0.00%	0.10%	0.10%
Excess and Surplus Lines Insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance
Gross amounts	$ 572	$ 510	$ 417
Ceded premiums earned	30	25	19
Assumed amounts from other companies	0	0	0
Premiums Earned, Net	$ 542	$ 485	$ 398
Percentage of amounts assumed to net	0.00%	0.00%	0.00%
Reinsurance assumed and other non segment
SEC Schedule, 12-17, Insurance Companies, Reinsurance
Gross amounts	$ 319	$ 262	$ 216
Ceded premiums earned	80	85	76
Assumed amounts from other companies	556	549	430
Premiums Earned, Net	$ 795	$ 726	$ 570
Percentage of amounts assumed to net	69.90%	75.60%	75.40%
Property, Liability and Casualty Insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance
Gross amounts	$ 7,407	$ 6,677	$ 5,996
Ceded premiums earned	331	314	255
Assumed amounts from other companies	569	561	443
Premiums Earned, Net	$ 7,645	$ 6,924	$ 6,184
Percentage of amounts assumed to net	7.40%	8.10%	7.20%
Life Insurance Segment
SEC Schedule, 12-17, Insurance Companies, Reinsurance
Gross amounts	$ 394	$ 379	$ 370
Ceded premiums earned	81	78	76
Assumed amounts from other companies	0	0	0
Premiums Earned, Net	$ 313	$ 301	$ 294
Percentage of amounts assumed to net	0.00%	0.00%	0.00%