Derivative Investments (Balance Sheet) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 93,367	$ 157,588
Liability Derivatives	116,802	155,902
Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Asset Derivatives	93,367	157,588
Liability Derivatives	116,802	155,902
Derivatives not designated as hedging instruments | Equity index options | Derivatives, Index Options
Derivatives, Fair Value [Line Items]
Asset Derivatives	93,367	157,588
Derivatives not designated as hedging instruments | Fixed-index products | Universal Life and Annuity Contracts
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ 116,802	$ 155,902