Fair Values of Financial Instruments (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) Basis_Points	Mar. 31, 2016 USD ($)	Dec. 31, 2016 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, transfers into Level 3, amount	0	$ 0
Liabilities, transfers into Level 3, amount	0	0
Assets, transfers out of Level 3, amount	0	0
Liabilities, transfers out of Level 3, amount	$ 0	$ 0
Fair Value, Sensitivity, Increase in Discount Rate by 10 Percent [Member]
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	$ (481,900)
Deferred policy scquisition costs and deferred sales inducements, combined balance, adjustment due to change in discount rate	$ (293,000)
Fair Value, Sensitivity, Decrease in Discount Rate by 10 Percent [Member]
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	$ 538,400
Deferred policy scquisition costs and deferred sales inducements, combined balance, adjustment due to change in discount rate	$ 320,300