SCHEDULE VI--SUPPLEMENTAL INFORMATION CONCERNING PROPERTY/CASUALTY INSURANCE OPERATIONS (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Deferred policy acquisition costs		$ 5,608	$ 1,172	$ 1,443
Reserves for unpaid claims and claim adjustment expenses		680,274	576,330	513,596
Discount if any deducted in Column C	[1]	0	0	2,110
Unearned premiums		53,085	21,694	25,291
Earned premiums		328,145	276,011	263,335
Net investment income		18,095	14,483	12,498
Claims and claim adjustment expenses incurred related to current year		228,303	172,645	165,812
Claims and claim adjustment expenses incurred related to prior years		19,215	13,836	(10,062)
Amortization of deferred policy acquisition costs		70,574	51,597	50,270
Paid claims and claim adjustment expenses		200,154	163,467	149,580
Net premiums written		$ 353,389	$ 271,752	$ 254,653
Loss reserve discounted present value cash flow pretax interest rate utilized				3.50%

[1] Loss reserves on certain reinsurance assumed and permanent total disability workers' compensation claims have been discounted to present value using pretax interest rates not exceeding 3.5% through 2015.