Sch III Supplementary Insurance Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	$ 330,324	$ 335,783	$ 220,760
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	6,821,890	6,427,014	6,147,935
Supplementary Insurance Information, Unearned Premiums	20,922	18,624	12,078
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	595,453	594,205	590,634
Supplementary Insurance Information, Premium Revenue	308,842	305,540	293,070
Supplementary Insurance Information, Net Investment Income	404,170	391,149	382,082
Investment Income, Nonoperating	6,550	(2,691)	2,270
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	416,268	393,588	374,416
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	28,225	35,220	33,303
Deferred Policy Acquisition Cost, Amortization Expense, Net Investment Gains (Losses)	(673)	225	189
Deferred Policy Acquisition Cost, Amortization Expense, Unrealized Investment Gains (Losses)	(562)	332	(125)
Supplementary Insurance Information, Other Operating Expense	107,742	108,448	104,955
Scenario, Actual [Member] | Annuity
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	88,762	85,819	82,778
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	3,827,295	3,550,364	3,370,109
Supplementary Insurance Information, Unearned Premiums	0	0	0
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	364,966	370,326	372,244
Supplementary Insurance Information, Premium Revenue	3,803	2,524	1,927
Supplementary Insurance Information, Net Investment Income	210,679	209,896	201,550
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	113,543	110,356	105,669
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	11,185	9,658	10,477
Supplementary Insurance Information, Other Operating Expense	23,733	22,456	22,275
Scenario, Actual [Member] | Life Insurance
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	267,545	248,333	232,020
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	2,573,276	2,473,357	2,372,108
Supplementary Insurance Information, Unearned Premiums	13,526	9,719	10,111
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	199,944	194,751	193,567
Supplementary Insurance Information, Premium Revenue	260,331	256,504	244,597
Supplementary Insurance Information, Net Investment Income	154,427	152,730	146,349
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	261,757	253,461	238,841
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	11,038	14,364	15,594
Supplementary Insurance Information, Other Operating Expense	75,100	76,167	72,641
Scenario, Actual [Member] | Corporate and Other
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	69,664	75,366	85,506
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	417,524	399,203	394,536
Supplementary Insurance Information, Unearned Premiums	11,611	12,257	13,428
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	30,543	29,128	24,823
Supplementary Insurance Information, Premium Revenue	44,716	46,519	46,547
Supplementary Insurance Information, Net Investment Income	32,514	31,214	31,913
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	37,296	32,346	29,470
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	6,078	11,316	6,929
Supplementary Insurance Information, Other Operating Expense	8,912	9,816	10,032
Scenario, Adjustment [Member]
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	(95,647)	(73,735)	(179,544)
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	3,795	4,090	11,182
Supplementary Insurance Information, Unearned Premiums	(4,215)	(3,352)	(11,461)
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	0	0	0
Supplementary Insurance Information, Premium Revenue	0	0	0
Unearned revenue reserve, amortization due to realized gains	(8)	(7)	(1)
Supplementary Insurance Information, Net Investment Income	0	0	0
Investment Income, Nonoperating	6,550	(2,691)	2,270
Deferred sales inducements, amortization due to realized gains losses	(32)	2	4
Deferred sales inducements, amortization due to unrealized gains losses	3,704	(2,577)	432
Deferred Policy Acquisition Cost, Amortization Expense, Net Investment Gains (Losses)	(638)	214	178
Deferred Policy Acquisition Cost, Amortization Expense, Unrealized Investment Gains (Losses)	(562)	332	(125)
Supplementary Insurance Information, Other Operating Expense	0	0	0
Present Value of Future Profits, amortization due to realized gains losses	$ (3)	$ 9	$ 7