Certain Long-Duration Contracts With Guarantees (Separate Account Investment Options) (Details) - Annuity Contracts - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Separate Account Investment [Line Items]
Separate Account Investment Options	$ 141,400,634	$ 139,147,485
Equity funds
Fair Value, Separate Account Investment [Line Items]
Separate Account Investment Options	83,132,748	82,506,787
Bond funds
Fair Value, Separate Account Investment [Line Items]
Separate Account Investment Options	55,850,849	53,763,563
Money market funds
Fair Value, Separate Account Investment [Line Items]
Separate Account Investment Options	$ 2,417,037	$ 2,877,135