Guaranteed Benefit Features (Account Balances Of Variable Annuity Contracts With Guarantees Invested In Separate Accounts) (Details) - Variable Annuity [Member] - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Account Balances Of Variable Annuity Contracts With Guarantees Invested In Separate Accounts [Line Items]
Total	$ 106,974	$ 125,350
Percent of total variable annuity separate account values	98.00%	98.00%
Domestic Equity [Member]
Account Balances Of Variable Annuity Contracts With Guarantees Invested In Separate Accounts [Line Items]
Total	$ 52,454	$ 64,093
International Equity [Member]
Account Balances Of Variable Annuity Contracts With Guarantees Invested In Separate Accounts [Line Items]
Total	15,998	19,852
Fixed Income [Member]
Account Balances Of Variable Annuity Contracts With Guarantees Invested In Separate Accounts [Line Items]
Total	$ 38,522	$ 41,405