Segment Information - Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 4,698	$ 4,711
Net investment income	509	459
Net realized capital gains (losses)	80	(231)
Other revenues	12	17
Total revenues	5,299	4,956
Corporate
Segment Reporting Information [Line Items]
Earned premiums and fee income	12	17
Commercial Lines | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	2,244	2,273
Commercial Lines | Operating Segments [Member] | Workers’ compensation
Segment Reporting Information [Line Items]
Earned premiums and fee income	738	816
Commercial Lines | Operating Segments [Member] | Liability
Segment Reporting Information [Line Items]
Earned premiums and fee income	375	343
Commercial Lines | Operating Segments [Member] | Marine
Segment Reporting Information [Line Items]
Earned premiums and fee income	58	65
Commercial Lines | Operating Segments [Member] | Package business
Segment Reporting Information [Line Items]
Earned premiums and fee income	393	377
Commercial Lines | Operating Segments [Member] | Property
Segment Reporting Information [Line Items]
Earned premiums and fee income	200	205
Commercial Lines | Operating Segments [Member] | Professional liability
Segment Reporting Information [Line Items]
Earned premiums and fee income	155	143
Commercial Lines | Operating Segments [Member] | Bond
Segment Reporting Information [Line Items]
Earned premiums and fee income	69	70
Commercial Lines | Operating Segments [Member] | Assumed reinsurance
Segment Reporting Information [Line Items]
Earned premiums and fee income	68	66
Commercial Lines | Operating Segments [Member] | Automobile
Segment Reporting Information [Line Items]
Earned premiums and fee income	188	188
Personal Lines | AARP Members [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	676	707
Personal Lines | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	742	783
Personal Lines | Operating Segments [Member] | Property
Segment Reporting Information [Line Items]
Earned premiums and fee income	230	240
Personal Lines | Operating Segments [Member] | Automobile
Segment Reporting Information [Line Items]
Earned premiums and fee income	512	543
Group Benefits | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	1,418	1,391
Group Benefits | Operating Segments [Member] | Group disability
Segment Reporting Information [Line Items]
Earned premiums and fee income	739	726
Group Benefits | Operating Segments [Member] | Group life
Segment Reporting Information [Line Items]
Earned premiums and fee income	602	607
Group Benefits | Operating Segments [Member] | Other
Segment Reporting Information [Line Items]
Earned premiums and fee income	77	58
Hartford Funds | Operating Segments [Member]
Segment Reporting Information [Line Items]
Earned premiums and fee income	282	247
Hartford Funds | Operating Segments [Member] | Mutual fund and Exchange-Traded Products ("ETP")
Segment Reporting Information [Line Items]
Earned premiums and fee income	259	225
Hartford Funds | Operating Segments [Member] | Talcott Resolution life and annuity separate accounts [2]
Segment Reporting Information [Line Items]
Earned premiums and fee income	$ 23	$ 22