Segment Information - Non-insurance Revenue from Customers (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	$ 323	$ 330	$ 941	$ 970
Other revenues	3	44	108	129
Non-insurance revenues with customers	346	359	1,006	1,052
Installment billing fees [Member] | Operating Segments [Member] | Commercial Lines
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	8	8	21	26
Installment billing fees [Member] | Operating Segments [Member] | Personal Lines
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	8	9	26	28
Insurance servicing revenues | Operating Segments [Member] | Personal Lines
Segment Reporting Information [Line Items]
Other revenues	23	23	63	65
Administrative services | Operating Segments [Member] | Group Benefits
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	44	45	132	135
Advisor, distribution and other management fees | Operating Segments [Member] | Hartford Funds
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	228	232	659	677
Other fees | Operating Segments [Member] | Hartford Funds
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	22	22	65	65
Investment management and other fees | Corporate
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	13	14	38	38
Transition service revenues | Corporate
Segment Reporting Information [Line Items]
Other revenues	$ 0	$ 6	$ 2	$ 18