Investments (Credit Quality Indicators For Commercial Mortgage Loans) (Details) - Commercial [Member] - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Mortgage Loans Credit Quality [Line Items]
Carrying value of mortgage loans on real estate	$ 15,606	$ 13,012
Percentage of total mortgage loans on real estate	100.00%	100.00%
Loan-to-value ratio, less than 65% [Member]
Mortgage Loans Credit Quality [Line Items]
Carrying value of mortgage loans on real estate	$ 14,206	$ 11,716
Percentage of total mortgage loans on real estate	91.00%	90.10%
Debt-service coverage ratio	2.35	2.30
Loan-to-value ratio, 65% to 74% [Member]
Mortgage Loans Credit Quality [Line Items]
Carrying value of mortgage loans on real estate	$ 1,399	$ 1,238
Percentage of total mortgage loans on real estate	9.00%	9.50%
Debt-service coverage ratio	1.87	1.76
Loan-to-value ratio, 75% to 100% [Member]
Mortgage Loans Credit Quality [Line Items]
Carrying value of mortgage loans on real estate	$ 1	$ 58
Percentage of total mortgage loans on real estate	0.00%	0.40%
Debt-service coverage ratio	1.09	0.95