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	$ 121,141,825	$ 117,887,885
Equity funds
Fair Value, Separate Account Investment [Line Items]
Separate Account Investment Options	68,436,773	67,526,437
Bond funds
Fair Value, Separate Account Investment [Line Items]
Separate Account Investment Options	51,126,536	48,484,071
Money market funds
Fair Value, Separate Account Investment [Line Items]
Separate Account Investment Options	$ 1,578,516	$ 1,877,377