SCHEDULE III -- SUPPLEMENTARY INSURANCE INFORMATION (Details) - Property/Casualty Insurance [Member] - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplementary Insurance Information [Abstract]
Deferred policy acquisition costs		$ 6,568	$ 5,608	$ 1,172
Reserves for unpaid claims and claim adjustment expenses		865,339	680,274	576,330
Unearned premiums		71,625	53,085	21,694
Other policy claims and benefits payable		0	0	0
Net premium earned		432,880	328,145	276,011
Net investment income	[1]	22,048	18,095	14,483
Benefits, claims, losses and settlement expenses	[1]	345,864	247,518	186,481
Amortization of deferred policy acquisition costs		78,105	70,574	51,597
Other operating expenses	[1],[2]	23,514	14,043	8,180
Net premiums written		$ 444,398	$ 353,389	$ 271,752

[1] Allocations of certain expenses have been made to investment income, settlement expenses and other operating expenses and are based on a number of assumptions and estimates. Results among these categories would change if different methods were applied.

[2] Commission allowances relating to reinsurance ceded are offset against other operating expenses.