Reinsurance - Summary of Premiums Earned and Losses Incurred (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Premiums earned:
Direct	$ 294,909	$ 275,044	$ 861,705	$ 808,531
Assumed	1,388	709	3,275	936
Ceded	(28,440)	(25,327)	(100,260)	(79,970)
Net premiums earned	267,857	250,426	764,720	729,497
Losses incurred:
Direct	36,755	(2,081)	102,835	12,642
Assumed	(34)	55	(110)	45
Ceded	(2,736)	508	(7,841)	(3,810)
Losses incurred, net	$ 33,985	$ (1,518)	$ 94,884	$ 8,877