Other Operating Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Operating Expenses [Abstract]
Amortization of gross deferred policy acquisition costs	$ 70,574	$ 51,597	$ 50,270
Other underwriting expenses	37,230	41,692	42,638
Reinsurance ceded credits	(23,187)	(33,512)	(28,956)
Total underwriting expenses	84,617	59,777	63,952
Operating expenses of non-insurance companies	28,977	29,685	26,621
Total other operating expenses	113,594	89,462	90,573
Director [Member] | Consulting Contract [Member]
Related Party Transaction [Line Items]
Annual fee	300
Incurred expenses	300	300
Director [Member] | Brokerage Agreement [Member]
Related Party Transaction [Line Items]
Total commission expense	$ 674	$ 419	$ 0