Segment Information - Net Income 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
Insurance Commissions and Fees	361	347	1,049	1,019
Net Investment Income	759	659	2,079	1,854
Net realized losses	(12)	(13)	(71)	(44)
Other Income	31	24	83	69
Total revenues	7,232	6,751	21,029	19,656
Benefits, Losses and Expenses	5,914	5,799	17,682	16,881
Segment Reporting, Other Segment Item, Amount	22	23	60	60
Income tax expense	238	185	642	517
Net income	1,080	767	2,705	2,258
Deferred Policy Acquisition Costs, Amortization Expense	639	585	1,871	1,691
Amortization of other intangible assets	18	18	53	53
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
Net realized losses	(33)	(27)	(96)	(75)
Other Income	25	23	71	67
Total revenues	7,181	6,709	20,919	19,546
Benefits, Losses and Expenses	5,827	5,713	17,427	16,628
Segment Reporting, Other Segment Item, Amount	22	23	60	60
Income tax expense	270	194	695	556
Net income	1,062	779	2,737	2,302
Deferred Policy Acquisition Costs, Amortization Expense	639	585	1,871	1,691
Amortization of other intangible assets	18	18	53	53
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
Net realized losses	(26)	(32)	(70)	(70)
Other Income	0	1	2	1
Total revenues	4,044	3,671	11,658	10,617
Benefits, Losses and Expenses	3,154	3,007	9,293	8,578
Segment Reporting, Other Segment Item, Amount	0	2	4	5
Income tax expense	180	134	478	393
Net income	710	528	1,883	1,641
Deferred Policy Acquisition Costs, Amortization Expense	559	512	1,636	1,477
Amortization of other intangible assets	7	7	21	21
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
Net realized losses	(4)	(2)	(10)	(9)
Other Income	25	22	69	66
Total revenues	1,046	971	3,045	2,786
Benefits, Losses and Expenses	851	915	2,697	2,669
Segment Reporting, Other Segment Item, Amount	21	17	55	51
Income tax expense	35	8	58	12
Net income	139	31	235	54
Deferred Policy Acquisition Costs, Amortization Expense	72	65	210	188
Amortization of other intangible assets	1	1	2	2
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
Net realized losses	0	0	(2)	(3)
Other Income	0	0	0	0
Total revenues	19	18	54	52
Benefits, Losses and Expenses	2	3	6	14
Segment Reporting, Other Segment Item, Amount	1	4	1	4
Income tax expense	4	1	9	5
Net income	12	10	38	29
Deferred Policy Acquisition Costs, Amortization Expense	0	0	0	0
Amortization of other intangible assets	0	0	0	0
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
Net realized losses	(8)	0	(28)	(8)
Other Income	0	0	0	0
Total revenues	1,786	1,774	5,341	5,296
Benefits, Losses and Expenses	1,606	1,580	4,805	4,753
Segment Reporting, Other Segment Item, Amount	0	0	0	0
Income tax expense	36	38	109	108
Net income	144	156	427	435
Deferred Policy Acquisition Costs, Amortization Expense	8	8	25	26
Amortization of other intangible assets	10	10	30	30
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
Net realized losses	5	7	14	15
Other Income	0	0	0	0
Total revenues	286	275	821	795
Benefits, Losses and Expenses	214	208	626	614
Segment Reporting, Other Segment Item, Amount	0	0	0	0
Income tax expense	15	13	41	38
Net income	57	54	154	143
Deferred Policy Acquisition Costs, Amortization Expense	0	0	0	0
Amortization of other intangible assets	0	0	0	0
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member]
Segment Reporting Information [Line Items]
Net Investment Income	14	17	42	47
Net realized losses	21	14	25	31
Other Income	6	1	12	2
Total revenues	51	42	110	110
Benefits, Losses and Expenses	65	63	195	193
Income tax expense	(32)	(9)	(53)	(39)
Net income	18	(12)	(32)	(44)
Deferred Policy Acquisition Costs, Amortization Expense	0	0	0	0
Amortization of other intangible assets	0	0	0	0
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] | Investment management and other fees
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	$ 10	$ 10	$ 31	$ 30