Schedule 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]
Deferred Policy Acquisition Costs	$ 164,112	$ 168,264	$ 139,719
Future Policy Benefits, Losses, Claims and Loss Expenses	2,474,399	2,376,253	2,417,201
Unearned Premiums	443,873	415,057	378,725
Earned Premium Revenue	1,023,401	930,890	828,330
Investment Income, Net	106,822	100,781	104,609
Benefits, Claims, Losses and Settlement Expenses	743,767	600,033	572,866
Amortization of Deferred Policy Acquisition Costs	211,013	186,817	167,449
Other Underwriting Expenses	103,421	102,937	94,871
Interest on Policyholders' Accounts	20,079	23,680	30,245
Premiums Written	964,970	887,874	804,715
Property and Casualty Insurance
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	93,362	90,547	72,861
Future Policy Benefits, Losses, Claims and Loss Expenses	1,123,896	1,003,895	969,437
Unearned Premiums	443,802	414,971	378,635
Earned Premium Revenue	936,131	851,695	766,939
Investment Income, Net	55,284	46,559	44,236
Benefits, Claims, Losses and Settlement Expenses	652,433	520,087	509,811
Amortization of Deferred Policy Acquisition Costs	202,892	180,183	161,310
Other Underwriting Expenses	83,540	83,631	79,117
Interest on Policyholders' Accounts	0	0	0
Premiums Written	964,970	887,874	804,715
Life Insurance
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	70,750	77,717	66,858
Future Policy Benefits, Losses, Claims and Loss Expenses	1,350,503	1,372,358	1,447,764
Unearned Premiums	71	86	90
Earned Premium Revenue	87,270	79,195	61,391
Investment Income, Net	51,538	54,222	60,373
Benefits, Claims, Losses and Settlement Expenses	91,334	79,946	63,055
Amortization of Deferred Policy Acquisition Costs	8,121	6,634	6,139
Other Underwriting Expenses	19,881	19,306	15,754
Interest on Policyholders' Accounts	20,079	23,680	30,245
Premiums Written	$ 0	$ 0	$ 0