Segment Information - Amortization of Deferred Policy Acquisition Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Amortization of deferred policy acquisition costs (DAC)	$ 1,622	$ 1,384	$ 1,372
Property and Casualty, Commercial Insurance [Member]
Segment Reporting Information [Line Items]
Amortization of deferred policy acquisition costs (DAC)	1,296	1,048	1,009
Personal Lines
Segment Reporting Information [Line Items]
Amortization of deferred policy acquisition costs (DAC)	259	275	309
Group Benefits
Segment Reporting Information [Line Items]
Amortization of deferred policy acquisition costs (DAC)	54	45	33
Hartford Funds
Segment Reporting Information [Line Items]
Amortization of deferred policy acquisition costs (DAC)	12	16	21
Corporate
Segment Reporting Information [Line Items]
Amortization of deferred policy acquisition costs (DAC)	$ 1	$ 0	$ 0