Segment Information - Reconciliation of Revenue from Segments to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 6,454	$ 6,081	$ 18,938	$ 17,777
Net investment income	759	659	2,079	1,854
Realized Investment Gains (Losses)	(12)	(13)	(71)	(44)
Other Income	31	24	83	69
Total revenues	7,232	6,751	21,029	19,656
P&C Personal Insurance \| AARP Members [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	855	817	2,520	2,360
Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	6,444	6,071	18,907	17,747
Net investment income	745	642	2,037	1,807
Realized Investment Gains (Losses)	(33)	(27)	(96)	(75)
Other Income	25	23	71	67
Total revenues	7,181	6,709	20,919	19,546
Operating Segments [Member] \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	3,551	3,260	10,321	9,451
Net investment income	519	442	1,405	1,235
Realized Investment Gains (Losses)	(26)	(32)	(70)	(70)
Other Income	0	1	2	1
Total revenues	4,044	3,671	11,658	10,617
Operating Segments [Member] \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	958	893	2,804	2,571
Net investment income	67	58	182	158
Realized Investment Gains (Losses)	(4)	(2)	(10)	(9)
Other Income	25	22	69	66
Total revenues	1,046	971	3,045	2,786
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	18	56	55
Realized Investment Gains (Losses)	0	0	(2)	(3)
Other Income	0	0	0	0
Total revenues	19	18	54	52
Operating Segments [Member] \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	1,658	1,655	4,989	4,959
Net investment income	136	119	380	345
Realized Investment Gains (Losses)	(8)	0	(28)	(8)
Other Income	0	0	0	0
Total revenues	1,786	1,774	5,341	5,296
Operating Segments [Member] \| Hartford Funds [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	277	263	793	766
Net investment income	4	5	14	14
Realized Investment Gains (Losses)	5	7	14	15
Other Income	0	0	0	0
Total revenues	286	275	821	795
Operating Segments [Member] \| Hartford Funds [Member] \| Mutual fund and ETF
Segment Reporting Information [Line Items]
Earned premiums and fee income	259	244	740	710
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	53	56
Operating Segments [Member] \| Workers' Compensation \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	938	933	2,773	2,776
Operating Segments [Member] \| General liability \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	633	575	1,826	1,641
Operating Segments [Member] \| Marine \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	72	71	209	205
Operating Segments [Member] \| Package business \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	683	593	1,961	1,714
Operating Segments [Member] \| Property \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	372	325	1,066	921
Operating Segments [Member] \| Property \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	319	272	907	780
Operating Segments [Member] \| Professional liability \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	224	209	638	612
Operating Segments [Member] \| Bond \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	88	82	256	240
Operating Segments [Member] \| Assumed reinsurance \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	218	194	660	555
Operating Segments [Member] \| Automobile \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	323	278	932	787
Operating Segments [Member] \| Automobile \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	639	621	1,897	1,791
Operating Segments [Member] \| Group disability \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	890	889	2,689	2,674
Operating Segments [Member] \| Group life \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	648	659	1,942	1,967
Operating Segments [Member] \| Other \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 120	$ 107	$ 358	$ 318