Segment Information - Reconciliation of Revenue from Segments to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 6,303	$ 5,917	$ 12,484	$ 11,696
Net investment income	664	602	1,320	1,195
Realized Investment Gains (Losses)	(10)	(59)	(59)	(31)
Other Income	30	26	52	45
Total revenues	6,987	6,486	13,797	12,905
P&C Personal Insurance \| AARP Members [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	841	788	1,660	1,550
Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	6,293	5,907	12,463	11,676
Net investment income	650	588	1,292	1,165
Realized Investment Gains (Losses)	(33)	(67)	(63)	(48)
Other Income	25	25	46	44
Total revenues	6,935	6,453	13,738	12,837
Operating Segments [Member] \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	3,435	3,132	6,770	6,191
Net investment income	449	402	886	793
Realized Investment Gains (Losses)	(20)	(50)	(44)	(38)
Other Income	1	0	2	0
Total revenues	3,865	3,484	7,614	6,946
Operating Segments [Member] \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	939	857	1,846	1,678
Net investment income	58	50	115	100
Realized Investment Gains (Losses)	(4)	(8)	(6)	(7)
Other Income	24	25	44	44
Total revenues	1,017	924	1,999	1,815
Operating Segments [Member] \| Property & Casualty Other Operations [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	0	0	0	0
Net investment income	19	19	37	37
Realized Investment Gains (Losses)	(2)	(3)	(2)	(3)
Other Income	0	0	0	0
Total revenues	17	16	35	34
Operating Segments [Member] \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	1,663	1,665	3,331	3,304
Net investment income	118	112	244	226
Realized Investment Gains (Losses)	(16)	(9)	(20)	(8)
Other Income	0	0	0	0
Total revenues	1,765	1,768	3,555	3,522
Operating Segments [Member] \| Hartford Funds [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	256	253	516	503
Net investment income	6	5	10	9
Realized Investment Gains (Losses)	9	3	9	8
Other Income	0	0	0	0
Total revenues	271	261	535	520
Operating Segments [Member] \| Hartford Funds [Member] \| Mutual fund and ETF
Segment Reporting Information [Line Items]
Earned premiums and fee income	239	235	481	466
Operating Segments [Member] \| Hartford Funds [Member] \| Third-party life and annuity separate accounts [3]
Segment Reporting Information [Line Items]
Earned premiums and fee income	17	18	35	37
Operating Segments [Member] \| Workers' Compensation \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	917	926	1,835	1,843
Operating Segments [Member] \| General liability \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	609	540	1,193	1,066
Operating Segments [Member] \| Marine \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	68	67	137	134
Operating Segments [Member] \| Package business \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	659	572	1,278	1,121
Operating Segments [Member] \| Property \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	355	306	694	596
Operating Segments [Member] \| Property \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	305	259	588	508
Operating Segments [Member] \| Professional liability \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	208	200	414	403
Operating Segments [Member] \| Bond \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	83	80	168	158
Operating Segments [Member] \| Assumed reinsurance \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	222	180	442	361
Operating Segments [Member] \| Automobile \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	314	261	609	509
Operating Segments [Member] \| Automobile \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	634	598	1,258	1,170
Operating Segments [Member] \| Group disability \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	899	895	1,799	1,785
Operating Segments [Member] \| Group life \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	644	663	1,294	1,308
Operating Segments [Member] \| Other \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 120	$ 107	$ 238	$ 211