Fair Values of Financial Instruments (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) Basis_Points	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Level 1 to Level 2 transfers, amount	$ 0	$ 0
Liabilities, Level 1 to Level 2 transfers, amount	0	0
Assets, Level 2 to Level 1 transfers, amount	0	0
Liabilities, Level 2 to Level 1 transfers, amount	0	0
Assets, Level 3 transfers, amount, net	0	0	$ 0
Liabilities, Level 3 transfers, amount, net	$ 0	$ 0	$ 0
Expected cost of annual call options	2.10%	2.90%	3.10%
Experience study on products with lifetime income benefit riders, period		10 years
Mean reversion period	8 years	20 years
Maximum | Measurement Input, Discount Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, sensitivity, discount rate adjustment (basis points) | Basis_Points	100
Fixed index annuities embedded derivative, adjustment due to change in discount rate	$ (614,100)
Deferred policy acquisition costs and deferred sales inducements, combined balance, adjustment due to change in discount rate	$ (258,300)
Minimum | Measurement Input, Discount Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, sensitivity, discount rate adjustment (basis points) | Basis_Points	(100)
Fixed index annuities embedded derivative, adjustment due to change in discount rate	$ 639,000
Deferred policy acquisition costs and deferred sales inducements, combined balance, adjustment due to change in discount rate	$ 278,300