Segment Information - Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total assets	$ 70,817	$ 62,307
Commercial Lines
Segment Reporting Information [Line Items]
Total assets	42,041	31,693
Personal Lines
Segment Reporting Information [Line Items]
Total assets	6,310	6,180
Property & Casualty Other Operations
Segment Reporting Information [Line Items]
Total assets	3,560	3,351
Group Benefits
Segment Reporting Information [Line Items]
Total assets	14,595	14,114
Hartford Funds
Segment Reporting Information [Line Items]
Total assets	634	583
Corporate
Segment Reporting Information [Line Items]
Total assets	$ 3,677	$ 6,386