Segment Information - Revenues (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 5,548	$ 5,151	$ 10,930	$ 10,164
Net investment income	540	541	1,055	1,050
Net realized losses	(64)	(338)	(71)	(483)
Other revenues	25	19	45	35
Total revenues	6,049	5,373	11,959	10,766
Corporate
Segment Reporting Information [Line Items]
Earned premiums and fee income	11	13	20	26
Commercial Lines \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	2,896	2,625	5,672	5,120
Commercial Lines \| Operating Segments [Member] \| Workers’ compensation
Segment Reporting Information [Line Items]
Earned premiums and fee income	924	869	1,822	1,704
Commercial Lines \| Operating Segments [Member] \| Liability
Segment Reporting Information [Line Items]
Earned premiums and fee income	502	453	988	877
Commercial Lines \| Operating Segments [Member] \| Marine
Segment Reporting Information [Line Items]
Earned premiums and fee income	66	54	125	115
Commercial Lines \| Operating Segments [Member] \| Package business
Segment Reporting Information [Line Items]
Earned premiums and fee income	514	449	998	884
Commercial Lines \| Operating Segments [Member] \| Property
Segment Reporting Information [Line Items]
Earned premiums and fee income	244	212	472	402
Commercial Lines \| Operating Segments [Member] \| Professional liability
Segment Reporting Information [Line Items]
Earned premiums and fee income	196	182	384	360
Commercial Lines \| Operating Segments [Member] \| Bond
Segment Reporting Information [Line Items]
Earned premiums and fee income	80	77	157	149
Commercial Lines \| Operating Segments [Member] \| Assumed reinsurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	143	118	281	218
Commercial Lines \| Operating Segments [Member] \| Automobile
Segment Reporting Information [Line Items]
Earned premiums and fee income	227	211	445	411
Personal Lines \| AARP Members [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	710	675	1,400	1,340
Personal Lines \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	767	733	1,514	1,461
Personal Lines \| Operating Segments [Member] \| Property
Segment Reporting Information [Line Items]
Earned premiums and fee income	239	231	471	460
Personal Lines \| Operating Segments [Member] \| Automobile
Segment Reporting Information [Line Items]
Earned premiums and fee income	528	502	1,043	1,001
Group Benefits \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	1,630	1,517	3,239	3,007
Group Benefits \| Operating Segments [Member] \| Group disability
Segment Reporting Information [Line Items]
Earned premiums and fee income	878	828	1,744	1,634
Group Benefits \| Operating Segments [Member] \| Group life
Segment Reporting Information [Line Items]
Earned premiums and fee income	650	599	1,293	1,196
Group Benefits \| Operating Segments [Member] \| Other
Segment Reporting Information [Line Items]
Earned premiums and fee income	102	90	202	177
Hartford Funds \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	244	263	485	550
Hartford Funds \| Operating Segments [Member] \| Mutual fund and ETF
Segment Reporting Information [Line Items]
Earned premiums and fee income	226	243	449	508
Hartford Funds \| Operating Segments [Member] \| Third-party life and annuity separate accounts
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 18	$ 20	$ 36	$ 42