Schedule IV - Reinsurance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Premium Earned:
Gross amount	$ 639,437	$ 567,089
Ceded to other companies	(278,509)	(207,732)
Assumed from other companies	2,159	1,680
Net premiums earned	$ 363,087	$ 361,037
Percentage of amount assumed to net	0.59%	0.47%
Property, Liability and Casualty Insurance Segment [Member]
Premium Earned:
Gross amount	$ 639,437	$ 567,089
Ceded to other companies	(278,509)	(207,732)
Assumed from other companies	2,159	1,680
Net premiums earned	$ 363,087	$ 361,037
Percentage of amount assumed to net	0.59%	0.47%