Reserve for Unpaid Losses and Loss Adjustment Expenses - Discounted Reserves, Group (Details) - Group Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted Average Discount Rate [Line Items]
Liability for unpaid losses and loss adjustment expenses, at undiscounted amounts	$ 8,636	$ 8,957	$ 9,071
Discount	(1,401)	(1,505)	(1,536)
Carrying value of liability for unpaid losses and loss adjustment expenses	$ 7,235	$ 7,452	$ 7,535
Weighted average discount rate	3.40%	3.40%	3.50%
Minimum
Weighted Average Discount Rate [Line Items]
Range of discount rates	2.10%	2.10%	2.10%
Maximum
Weighted Average Discount Rate [Line Items]
Range of discount rates	8.00%	8.00%	8.00%