Schedule III. Supplementary Insurance Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	$ 159,253	$ 164,112	$ 168,264
Future Policy Benefits, Losses, Claims and Loss Expenses	2,544,584	2,474,399	2,376,253
Unearned Premiums	465,458	443,873	415,057
Earned Premium Revenue	1,058,860	1,023,401	930,890
Investment Income, Net	100,910	106,822	100,781
Benefits, Claims, Losses and Settlement Expenses	793,796	743,767	600,033
Amortization of Deferred Policy Acquisition Costs	212,927	211,013	186,817
Other Underwriting Expenses	116,909	103,421	102,937
Interest on Policyholders' Accounts	18,525	20,079	23,680
Premiums Written	1,019,113	964,970	887,874
Continuing Operations - Property and Casualty Insurance
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	88,102	93,362	90,547
Future Policy Benefits, Losses, Claims and Loss Expenses	1,224,183	1,123,896	1,003,895
Unearned Premiums	465,391	443,802	414,971
Earned Premium Revenue	997,492	936,131	851,695
Investment Income, Net	51,190	55,284	46,559
Benefits, Claims, Losses and Settlement Expenses	725,713	652,433	520,087
Amortization of Deferred Policy Acquisition Costs	207,746	202,892	180,183
Other Underwriting Expenses	103,628	83,540	83,631
Interest on Policyholders' Accounts	0	0	0
Premiums Written	1,019,113	964,970	887,874
Discontinued Operations | Discontinued Operations - Life Insurance
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	71,151	70,750	77,717
Future Policy Benefits, Losses, Claims and Loss Expenses	1,320,401	1,350,503	1,372,358
Unearned Premiums	67	71	86
Earned Premium Revenue	61,368	87,270	79,195
Investment Income, Net	49,720	51,538	54,222
Benefits, Claims, Losses and Settlement Expenses	68,083	91,334	79,946
Amortization of Deferred Policy Acquisition Costs	5,181	8,121	6,634
Other Underwriting Expenses	13,281	19,881	19,306
Interest on Policyholders' Accounts	18,525	20,079	23,680
Premiums Written	$ 0	$ 0	$ 0