Reinsurance - Summary of Premiums Earned and Losses Incurred (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Premiums earned:
Direct	$ 268,709	$ 270,718	$ 789,317	$ 789,671
Assumed	312	152	472	542
Ceded	(31,938)	(33,494)	(92,467)	(100,040)
Net premiums earned	237,083	237,376	697,322	690,173
Losses incurred:
Direct	35,313	69,579	99,122	216,874
Assumed	(97)	241	69	681
Ceded	(5,469)	(8,923)	(14,486)	(25,056)
Losses incurred, net	$ 29,747	$ 60,897	$ 84,705	$ 192,499