Segment Information - Non-insurance Revenue from Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	$ 355	$ 320
Other revenues	12	17
Non-insurance revenues with customers	374	341
Installment billing fees [Member] | Operating Segments [Member] | Commercial Lines
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	9	8
Installment billing fees [Member] | Operating Segments [Member] | Personal Lines
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	8	9
Insurance servicing revenues | Operating Segments [Member] | Personal Lines
Segment Reporting Information [Line Items]
Other revenues	19	19
Administrative services | Operating Segments [Member] | Group Benefits
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	44	43
Advisor, distribution and other management fees | Operating Segments [Member] | Hartford Funds
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	257	224
Other fees | Operating Segments [Member] | Hartford Funds
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	25	23
Investment management and other fees | Corporate
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	12	13
Transition service revenues | Corporate
Segment Reporting Information [Line Items]
Other revenues	$ 0	$ 2