Segment Information - Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 5,640	$ 5,238	$ 16,570	$ 15,402
Net investment income	597	487	1,652	1,537
Net realized losses	(90)	(166)	(161)	(649)
Other revenues	21	21	66	56
Total revenues	6,168	5,580	18,127	16,346
Corporate
Segment Reporting Information [Line Items]
Earned premiums and fee income	10	11	30	37
Commercial Lines | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	2,962	2,713	8,634	7,833
Commercial Lines | Operating Segments [Member] | Workers’ compensation
Segment Reporting Information [Line Items]
Earned premiums and fee income	919	892	2,741	2,596
Commercial Lines | Operating Segments [Member] | Liability
Segment Reporting Information [Line Items]
Earned premiums and fee income	522	471	1,510	1,348
Commercial Lines | Operating Segments [Member] | Marine
Segment Reporting Information [Line Items]
Earned premiums and fee income	67	60	192	175
Commercial Lines | Operating Segments [Member] | Package business
Segment Reporting Information [Line Items]
Earned premiums and fee income	534	473	1,532	1,357
Commercial Lines | Operating Segments [Member] | Property
Segment Reporting Information [Line Items]
Earned premiums and fee income	250	218	722	620
Commercial Lines | Operating Segments [Member] | Professional liability
Segment Reporting Information [Line Items]
Earned premiums and fee income	198	189	582	549
Commercial Lines | Operating Segments [Member] | Bond
Segment Reporting Information [Line Items]
Earned premiums and fee income	82	77	239	226
Commercial Lines | Operating Segments [Member] | Assumed reinsurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	156	119	437	337
Commercial Lines | Operating Segments [Member] | Automobile
Segment Reporting Information [Line Items]
Earned premiums and fee income	234	214	679	625
Personal Lines | AARP Members [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	731	695	2,100	2,000
Personal Lines | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	791	757	2,305	2,218
Personal Lines | Operating Segments [Member] | Property
Segment Reporting Information [Line Items]
Earned premiums and fee income	245	235	716	695
Personal Lines | Operating Segments [Member] | Automobile
Segment Reporting Information [Line Items]
Earned premiums and fee income	546	522	1,589	1,523
Group Benefits | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	1,629	1,504	4,868	4,511
Group Benefits | Operating Segments [Member] | Group disability
Segment Reporting Information [Line Items]
Earned premiums and fee income	884	823	2,628	2,457
Group Benefits | Operating Segments [Member] | Group life
Segment Reporting Information [Line Items]
Earned premiums and fee income	643	593	1,936	1,789
Group Benefits | Operating Segments [Member] | Other
Segment Reporting Information [Line Items]
Earned premiums and fee income	102	88	304	265
Hartford Funds | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	248	253	733	803
Hartford Funds | Operating Segments [Member] | Mutual fund and ETF
Segment Reporting Information [Line Items]
Earned premiums and fee income	229	234	678	742
Hartford Funds | Operating Segments [Member] | Third-party life and annuity separate accounts
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 19	$ 19	$ 55	$ 61