Segment Information - Reconciliation of Revenue from Segments to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 6,181	$ 5,779
Net investment income	656	593
Realized Investment Gains (Losses)	(49)	28
Other Income	22	19
Total revenues	6,810	6,419
P&C Personal Insurance \| AARP Members [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	822	758
Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	6,170	5,769
Net investment income	642	577
Realized Investment Gains (Losses)	(30)	19
Other Income	21	19
Total revenues	6,803	6,384
Operating Segments [Member] \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	3,335	3,059
Net investment income	437	391
Realized Investment Gains (Losses)	(24)	12
Other Income	1	0
Total revenues	3,749	3,462
Operating Segments [Member] \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	907	821
Net investment income	57	50
Realized Investment Gains (Losses)	(2)	1
Other Income	20	19
Total revenues	982	891
Operating Segments [Member] \| Property & Casualty Other Operations [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	0	0
Net investment income	18	18
Realized Investment Gains (Losses)	0	0
Other Income	0	0
Total revenues	18	18
Operating Segments [Member] \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	1,668	1,639
Net investment income	126	114
Realized Investment Gains (Losses)	(4)	1
Other Income	0	0
Total revenues	1,790	1,754
Operating Segments [Member] \| Hartford Funds [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	260	250
Net investment income	4	4
Realized Investment Gains (Losses)	0	5
Other Income	0	0
Total revenues	264	259
Operating Segments [Member] \| Hartford Funds [Member] \| Mutual fund and ETF
Segment Reporting Information [Line Items]
Earned premiums and fee income	242	231
Operating Segments [Member] \| Hartford Funds [Member] \| Third-party life and annuity separate accounts [3]
Segment Reporting Information [Line Items]
Earned premiums and fee income	18	19
Operating Segments [Member] \| Workers' Compensation \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	918	917
Operating Segments [Member] \| General liability \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	584	526
Operating Segments [Member] \| Marine \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	69	67
Operating Segments [Member] \| Package business \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	619	549
Operating Segments [Member] \| Property \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	339	290
Operating Segments [Member] \| Property \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	283	249
Operating Segments [Member] \| Professional liability \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	206	203
Operating Segments [Member] \| Bond \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	85	78
Operating Segments [Member] \| Assumed reinsurance \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	220	181
Operating Segments [Member] \| Automobile \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	295	248
Operating Segments [Member] \| Automobile \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	624	572
Operating Segments [Member] \| Group disability \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	900	890
Operating Segments [Member] \| Group life \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	650	645
Operating Segments [Member] \| Other \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 118	$ 104