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Accrued Restructuring and Other Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs	$ 104	$ 0	$ 0
Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring	(50)
Employee Severance \| Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring	(19)
Information Technology \| Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring	(2)
Professional fees and other expenses \| Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring	(29)
Other Operating Income (Expense) [Member] \| Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs	104
Other Operating Income (Expense) [Member] \| Employee Severance \| Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs	73
Other Operating Income (Expense) [Member] \| Information Technology \| Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs	2
Other Operating Income (Expense) [Member] \| Professional fees and other expenses \| Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs	29
Other liabilities \| Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance	0
Restructuring Reserve, Ending Balance	54	0
Other liabilities \| Employee Severance \| Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance	0
Restructuring Reserve, Ending Balance	54	0
Other liabilities \| Information Technology \| Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance	0
Restructuring Reserve, Ending Balance	0	0
Other liabilities \| Professional fees and other expenses \| Hartford Next Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance	0
Restructuring Reserve, Ending Balance	$ 0	$ 0