Underwriting, Acquisition and Insurance Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Underwriting, Acquisition and Insurance Expenses [Abstract]
Gross commissions	$ 8,756	$ 7,544	$ 17,135	$ 14,693
Ceding commissions	(2,464)	(2,466)	(4,908)	(4,812)
Other operating expenses	6,227	5,414	12,690	11,905
Underwriting, acquisition, and insurance expenses	12,519	10,492	24,917	21,786
Salaries, bonuses and employee benefits	$ 5,300	$ 4,500	$ 10,300	$ 9,500