Fair Value of Financial Instruments (Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	$ 2,946,059	$ 3,041,131
Equity securities	17,491	18,478
Derivatives, index options	14,684	194,731
Total assets	2,978,234	3,254,340
Policyholder account balances	44,781	211,159
Other liabilities	11,923	15,242
Total liabilities	$ 56,704	226,401
Percent of total (in percentage)	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	17,491	18,478
Derivatives, index options	0	0
Total assets	17,491	18,478
Policyholder account balances	0	0
Other liabilities	0	0
Total liabilities	$ 0	0
Percent of total (in percentage)	0.60%
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	$ 2,946,059	3,041,131
Equity securities	0	0
Derivatives, index options	0	0
Total assets	2,946,059	3,041,131
Policyholder account balances	0	0
Other liabilities	0	0
Total liabilities	$ 0	0
Percent of total (in percentage)	98.90%
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	14,684	194,731
Total assets	14,684	194,731
Policyholder account balances	44,781	211,159
Other liabilities	11,923	15,242
Total liabilities	$ 56,704	$ 226,401
Percent of total (in percentage)	0.50%
Priced by Third-Party Vendors
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	$ 2,946,059
Equity securities	17,491
Derivatives, index options	14,684
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
Equity securities	17,491
Derivatives, index options	0
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	2,946,059
Equity securities	0
Derivatives, index options	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
Equity securities	0
Derivatives, index options	14,684
Priced Internally
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	0
Equity securities	0
Derivatives, index options	0
Priced Internally | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	0
Equity securities	0
Derivatives, index options	0
Priced Internally | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	0
Equity securities	0
Derivatives, index options	0
Priced Internally | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available for sale	0
Equity securities	0
Derivatives, index options	$ 0