Segment Information - Income Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Income tax expense	$ 475	$ 268	$ 985
Commercial Lines
Segment Reporting Information [Line Items]
Income tax expense	270	267	377
Personal Lines
Segment Reporting Information [Line Items]
Income tax expense	76	(19)	26
Property & Casualty Other Operations
Segment Reporting Information [Line Items]
Income tax expense	12	(7)	24
Group Benefits
Segment Reporting Information [Line Items]
Income tax expense	126	84	38
Hartford Funds
Segment Reporting Information [Line Items]
Income tax expense	37	38	63
Corporate
Segment Reporting Information [Line Items]
Income tax expense	$ (46)	$ (95)	$ 457