Segment Information - Reconciliation of Revenue from Segments to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 6,515	$ 6,181
Net investment income	739	656
Realized Investment Gains (Losses)	(55)	(49)
Other Income	27	22
Total revenues	7,226	6,810
P&C Personal Insurance \| AARP Members [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	806	822
Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	6,505	6,170
Net investment income	723	642
Realized Investment Gains (Losses)	(38)	(30)
Other Income	22	21
Total revenues	7,212	6,803
Operating Segments [Member] \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	3,584	3,335
Net investment income	505	437
Realized Investment Gains (Losses)	(19)	(24)
Other Income	0	1
Total revenues	4,070	3,749
Operating Segments [Member] \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	915	907
Net investment income	62	57
Realized Investment Gains (Losses)	(4)	(2)
Other Income	22	20
Total revenues	995	982
Operating Segments [Member] \| Property & Casualty Other Operations [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	0	0
Net investment income	20	18
Realized Investment Gains (Losses)	(1)	0
Other Income	0	0
Total revenues	19	18
Operating Segments [Member] \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	1,723	1,668
Net investment income	131	126
Realized Investment Gains (Losses)	(11)	(4)
Other Income	0	0
Total revenues	1,843	1,790
Operating Segments [Member] \| Hartford Funds [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	283	260
Net investment income	5	4
Realized Investment Gains (Losses)	(3)	0
Other Income	0	0
Total revenues	285	264
Operating Segments [Member] \| Hartford Funds [Member] \| Mutual fund and ETF
Segment Reporting Information [Line Items]
Earned premiums and fee income	266	242
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
Operating Segments [Member] \| Workers' Compensation \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	921	918
Operating Segments [Member] \| General liability \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	641	584
Operating Segments [Member] \| Marine \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	72	69
Operating Segments [Member] \| Package business \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	706	619
Operating Segments [Member] \| Property \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	372	339
Operating Segments [Member] \| Property \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	317	283
Operating Segments [Member] \| Professional liability \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	215	206
Operating Segments [Member] \| Bond \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	83	85
Operating Segments [Member] \| Assumed reinsurance \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	230	220
Operating Segments [Member] \| Automobile \| P&C Business Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	344	295
Operating Segments [Member] \| Automobile \| P&C Personal Insurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	598	624
Operating Segments [Member] \| Group disability \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	927	900
Operating Segments [Member] \| Group life \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	661	650
Operating Segments [Member] \| Other \| Employee Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 135	$ 118

HARTFORD INSURANCE GROUP, INC. 10-Q