Policyholders' Liabilities (Policyholders' Account Balances) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Liability for Policyholders' Account Balances, by Product Segment [Line Items]
Total policyholders’ account balances	$ 9,181,459	$ 6,180,359
Interest-sensitive life contracts
Liability for Policyholders' Account Balances, by Product Segment [Line Items]
Total policyholders’ account balances	13,842	14,391
Individual annuities
Liability for Policyholders' Account Balances, by Product Segment [Line Items]
Total policyholders’ account balances	8,760,543	5,716,052
Guaranteed interest accounts
Liability for Policyholders' Account Balances, by Product Segment [Line Items]
Total policyholders’ account balances	$ 407,074	$ 449,916