Reinsurance - Summary of Premiums Earned and Losses Incurred (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Premiums earned:
Direct	$ 261,180	$ 263,566	$ 520,608	$ 518,953
Assumed	62	182	160	390
Ceded	(30,106)	(32,292)	(60,529)	(66,546)
Net premiums earned	231,136	231,456	460,239	452,797
Losses incurred:
Direct	31,396	54,863	63,809	147,295
Assumed	61	339	166	440
Ceded	(4,118)	(8,612)	(9,017)	(16,133)
Losses incurred, net	$ 27,339	$ 46,590	$ 54,958	$ 131,602