Policyholders' Liabilities (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Policyholder Account Balances	$ 4,736,889	$ 2,416,125
Domestic individual non-participating life insurance | Minimum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Future Policy Benefits, Interest Rate	0.00%
Domestic individual non-participating life insurance | Maximum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Future Policy Benefits, Interest Rate	0.00%
Individual and group annuities and supplementary contracts
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Percentage Of Reserves Based On Interest Rates In Excess Of 8 Percent	0.10%
Individual and group annuities and supplementary contracts | Minimum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Future Policy Benefits, Interest Rate	0.00%
Individual and group annuities and supplementary contracts | Maximum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Future Policy Benefits, Interest Rate	8.30%
Other contract liabilities | Minimum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Future Policy Benefits, Interest Rate	1.40%
Other contract liabilities | Maximum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Future Policy Benefits, Interest Rate	4.10%
Interest-sensitive life contracts
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Policyholder Account Balances	$ 15,666	15,832
Interest-sensitive life contracts | Minimum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Policyholders Account Balances, Interest rate	3.50%
Interest-sensitive life contracts | Maximum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Policyholders Account Balances, Interest rate	6.00%
Individual annuities
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Policyholder Account Balances	$ 1,441,126	1,337,876
Individual annuities | Minimum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Policyholders Account Balances, Interest rate	0.00%
Individual annuities | Maximum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Policyholders Account Balances, Interest rate	6.50%
Guaranteed interest accounts
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Policyholder Account Balances	$ 893,419	$ 1,062,417
Guaranteed interest accounts | Minimum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Policyholders Account Balances, Interest rate	0.00%
Guaranteed interest accounts | Maximum
Liability for Future Policy Benefit and Policyholders' Account Balances, by Product Segment [Line Items]
Liability for Policyholders Account Balances, Interest rate	5.80%