Investments (Fair Value Below Amortized Cost of Gross Unrealized Losses for Fixed Maturity Securities) (Details) - USD ($) $ in Millions	6 Months Ended	9 Months Ended
	Jun. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Gross unrealized losses with number of securities [Line Items]
Document Period End Date	Jun. 30, 2021
Gross Unrealized Losses	$ 267	$ 197
% of Total	100.00%		100.00%
Less than 20%
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 213	133
% of Total	79.80%		67.50%
20% or more for less than six months
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 2	42
% of Total	0.70%		21.30%
20% or more for six months or greater
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 52	$ 22
% of Total	19.50%		11.20%