Fair Value of Financial Instruments (Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	$ 3,174,260	$ 3,356,945
Equity securities	15,984	23,594
Derivatives, index options	24,335	157,588
Other invested assets	2	2
Total assets	3,214,581	3,538,129
Policyholder account balances	61,625	155,902
Other liabilities	7,255	15,301
Total liabilities	$ 68,880	$ 171,203
Percent of total	100.00%	100.00%
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	$ 0	$ 0
Equity securities	15,984	23,594
Derivatives, index options	0	0
Other invested assets	2	2
Total assets	15,986	23,596
Policyholder account balances	0	0
Other liabilities	0	0
Total liabilities	$ 0	$ 0
Percent of total	0.50%	0.70%
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	$ 3,174,260	$ 3,356,945
Equity securities	0	0
Derivatives, index options	0	0
Other invested assets	0	0
Total assets	3,174,260	3,356,945
Policyholder account balances	0	0
Other liabilities	0	0
Total liabilities	$ 0	$ 0
Percent of total	98.70%	94.80%
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	$ 0	$ 0
Equity securities	0	0
Derivatives, index options	24,335	157,588
Other invested assets	0	0
Total assets	24,335	157,588
Policyholder account balances	61,625	155,902
Other liabilities	7,255	15,301
Total liabilities	$ 68,880	$ 171,203
Percent of total	0.80%	4.50%
Priced by Third-Party Vendors
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	$ 3,174,260	$ 3,356,945
Equity securities	15,984	23,594
Derivatives, index options	24,335	157,588
Other invested assets	2	2
Priced by Third-Party Vendors | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	0	0
Equity securities	15,984	23,594
Derivatives, index options	0	0
Other invested assets	2	2
Priced by Third-Party Vendors | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	3,174,260	3,356,945
Equity securities	0	0
Derivatives, index options	0	0
Other invested assets	0	0
Priced by Third-Party Vendors | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	0	0
Equity securities	0	0
Derivatives, index options	24,335	157,588
Other invested assets	0	0
Priced Internally
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	0	0
Equity securities	0	0
Derivatives, index options	0	0
Other invested assets	0	0
Priced Internally | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	0	0
Equity securities	0	0
Derivatives, index options	0	0
Other invested assets	0	0
Priced Internally | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	0	0
Equity securities	0	0
Derivatives, index options	0	0
Other invested assets	0	0
Priced Internally | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	0	0
Equity securities	0	0
Derivatives, index options	0	0
Other invested assets	$ 0	$ 0