Fair Value of Financial Instruments (Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale	$ 3,410,656	$ 3,356,945
Equity securities	18,610	23,594
Derivatives, index options	93,367	157,588
Other invested assets	1	2
Total assets	3,522,634	3,538,129
Policyholder account balances	116,802	155,902
Other liabilities	4,951	15,301
Total liabilities	$ 121,753	$ 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	18,610	23,594
Derivatives, index options	0	0
Other invested assets	1	2
Total assets	18,611	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	$ 3,410,656	$ 3,356,945
Equity securities	0	0
Derivatives, index options	0	0
Other invested assets	0	0
Total assets	3,410,656	3,356,945
Policyholder account balances	0	0
Other liabilities	0	0
Total liabilities	$ 0	$ 0
Percent of total	96.80%	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	93,367	157,588
Other invested assets	0	0
Total assets	93,367	157,588
Policyholder account balances	116,802	155,902
Other liabilities	4,951	15,301
Total liabilities	$ 121,753	$ 171,203
Percent of total	2.70%	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	$ 3,410,656	$ 3,356,945
Equity securities	18,610	23,594
Derivatives, index options	93,367	157,588
Other invested assets	1	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	18,610	23,594
Derivatives, index options	0	0
Other invested assets	1	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	3,410,656	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	93,367	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