Investments (Fair Value Below Amortized Cost of Gross Unrealized Losses for Fixed Maturity and Equity Securities) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Gross unrealized losses with number of securities [Line Items]
Document Period End Date	Mar. 31, 2020
Gross Unrealized Losses	$ 1,461	$ 110
% of Total	100.00%	100.00%
Less than 20%
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 1,052	$ 76
% of Total	72.00%	69.10%
20% or more for less than six months
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 409	$ 20
% of Total	28.00%	18.20%
20% or more for six months or greater
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 0	$ 14
% of Total	0.00%	12.70%