Schedule IV - Reinsurance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Consolidated earned premiums [Abstract]
Gross amount	$ 399,660	$ 384,993	$ 382,300
Ceded to other companies	455,395	437,881	426,946
Assumed from other companies	700,918	660,046	637,054
Net amount	$ 645,183	$ 607,158	$ 592,408
Percentage of amount assumed to net	108.60%	108.70%	107.50%