Fair Value Valuation of Financial Instruments Not Reported at Fair Value by Hierarchy Level (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans	$ 816,471	$ 744,303
Policy loans	188,254	185,784
Other investments	16,145	9,518
Liabilities related to separate accounts	597,072	625,257
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Future policy benefits	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	9,360	2,331
Future policy benefits	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Future policy benefits		9,374
Portion at Other than Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans	840,337	780,624
Policy loans	230,656	230,153
Other investments	1,912
Assets, Fair Value Disclosure	1,072,905	1,010,777
Future policy benefits	3,887,399	3,608,771
Supplementary contracts without life contingencies	330,633	339,717
Advance premiums and other deposits	257,171	245,269
Short-term debt		15,000
Long-term debt	67,599	68,133
Liabilities related to separate accounts	593,760	620,676
Liabilities, Fair Value Disclosure	5,136,562	4,897,566
Portion at Other than Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans	0	0
Policy loans	0	0
Assets, Fair Value Disclosure	0	0
Future policy benefits	0	0
Supplementary contracts without life contingencies	0	0
Advance premiums and other deposits	0	0
Short-term debt		0
Long-term debt	0	0
Liabilities related to separate accounts	0	0
Liabilities, Fair Value Disclosure	0	0
Portion at Other than Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans	0	0
Policy loans	0	0
Assets, Fair Value Disclosure	0	0
Future policy benefits	0	0
Supplementary contracts without life contingencies	0	0
Advance premiums and other deposits	0	0
Short-term debt		0
Long-term debt	0	0
Liabilities related to separate accounts	0	0
Liabilities, Fair Value Disclosure	0	0
Portion at Other than Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans	840,337	780,624
Policy loans	230,656	230,153
Other investments	1,912
Assets, Fair Value Disclosure	1,072,905	1,010,777
Future policy benefits	3,887,399	3,608,771
Supplementary contracts without life contingencies	330,633	339,717
Advance premiums and other deposits	257,171	245,269
Short-term debt		15,000
Long-term debt	67,599	68,133
Liabilities related to separate accounts	593,760	620,676
Liabilities, Fair Value Disclosure	$ 5,136,562	$ 4,897,566