Segment Information - Net Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net investment income	$ 2,313	$ 1,846	$ 1,951
Operating Segments | P&C Commercial Lines
Segment Reporting Information [Line Items]
Net investment income	1,502	1,160	1,129
Operating Segments | P&C Personal Lines
Segment Reporting Information [Line Items]
Net investment income	157	157	179
Operating Segments | Property & Casualty Other Operations
Segment Reporting Information [Line Items]
Net investment income	75	55	84
Operating Segments | Group Benefits [Member]
Segment Reporting Information [Line Items]
Net investment income	550	448	486
Operating Segments | Hartford Funds
Segment Reporting Information [Line Items]
Net investment income	5	4	7
Corporate
Segment Reporting Information [Line Items]
Net investment income	$ 24	$ 22	$ 66