Segment Information - Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 4,532	$ 4,492	$ 9,243	$ 8,746
Net investment income	339	488	798	958
Net realized capital gains	109	80	(122)	243
Other revenues	88	32	105	85
Total revenues	5,068	5,092	10,024	10,032
Corporate
Segment Reporting Information [Line Items]
Earned premiums and fee income	17	12	34	25
Commercial Lines
Segment Reporting Information [Line Items]
Earned premiums and fee income	2,162	1,996	4,435	3,782
Commercial Lines | Workers’ compensation
Segment Reporting Information [Line Items]
Earned premiums and fee income	720	832	1,536	1,656
Commercial Lines | Liability
Segment Reporting Information [Line Items]
Earned premiums and fee income	337	233	680	401
Commercial Lines | Marine
Segment Reporting Information [Line Items]
Earned premiums and fee income	67	27	132	27
Commercial Lines | Package business
Segment Reporting Information [Line Items]
Earned premiums and fee income	383	365	760	717
Commercial Lines | Property
Segment Reporting Information [Line Items]
Earned premiums and fee income	185	175	390	331
Commercial Lines | Professional liability
Segment Reporting Information [Line Items]
Earned premiums and fee income	149	98	292	166
Commercial Lines | Bond
Segment Reporting Information [Line Items]
Earned premiums and fee income	68	65	138	125
Commercial Lines | Assumed reinsurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	72	29	138	29
Commercial Lines | Automobile
Segment Reporting Information [Line Items]
Earned premiums and fee income	181	172	369	330
Personal Lines
Segment Reporting Information [Line Items]
Earned premiums and fee income	703	811	1,486	1,619
Personal Lines | AARP Members [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	633	726	1,300	1,400
Personal Lines | Property
Segment Reporting Information [Line Items]
Earned premiums and fee income	241	246	481	493
Personal Lines | Automobile
Segment Reporting Information [Line Items]
Earned premiums and fee income	462	565	1,005	1,126
Group Benefits
Segment Reporting Information [Line Items]
Earned premiums and fee income	1,423	1,422	2,814	2,831
Group Benefits | Group disability
Segment Reporting Information [Line Items]
Earned premiums and fee income	719	723	1,445	1,427
Group Benefits | Group life
Segment Reporting Information [Line Items]
Earned premiums and fee income	632	638	1,239	1,281
Group Benefits | Other
Segment Reporting Information [Line Items]
Earned premiums and fee income	72	61	130	123
Hartford Funds
Segment Reporting Information [Line Items]
Earned premiums and fee income	227	251	474	489
Hartford Funds | Mutual fund and Exchange-Traded Products (ETP)
Segment Reporting Information [Line Items]
Earned premiums and fee income	207	227	432	443
Hartford Funds | Talcott Resolution life and annuity separate accounts [2]
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 20	$ 24	$ 42	$ 46