Segment Information - Net Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Net income	$ 249	$ 273
Preferred stock dividends	5	5
Net income available to common stockholders	244	268
Corporate
Segment Reporting Information [Line Items]
Net income	(58)	(91)
Commercial Lines | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net income	129	121
Personal Lines | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net income	135	98
Property & Casualty Other Operations | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net income	(13)	5
Group Benefits | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net income	9	104
Hartford Funds | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net income	$ 47	$ 36