Reinsurance Written and Earned Premiums (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Written Premiums
Direct	$ 852,404	$ 843,675	$ 827,316
Assumed	32,391	32,403	34,214
Ceded	(90,386)	(89,166)	(80,476)
Net written premiums	794,409	786,912	781,054
Earned Premiums
Direct	845,102	836,759	818,804
Assumed	32,853	32,196	32,502
Ceded	(89,178)	(87,368)	(76,886)
Net earned premiums	788,777	781,587	774,420
Loss and LAE
Direct	562,192	538,569	517,146
Assumed	28,529	28,815	28,003
Ceded	(80,875)	(81,871)	(41,262)
Net loss and LAE	$ 509,846	$ 485,513	$ 503,887