Reserves for Unpaid Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Net reserves for unpaid losses and loss adjustment expenses, beginning of year	$ 267,493	$ 194,602
Commutations of MLQS	0	27,929
Adjusted net reserves for losses and loss adjustment expenses, beginning of year	267,493	222,531
Incurred losses and loss adjustment expenses:
Current year	62,389	52,902
Prior years	(3,523)	(8,936)
Total net losses and loss adjustment expenses incurred	58,866	43,966
Payments:
Current year	1,858	2,185
Prior years	33,309	19,508
Total payments	35,167	21,693
Net reserves for unpaid losses and loss adjustment expenses, end of period	291,192	244,804
Reinsurance recoverable on unpaid losses	53,373	39,624
Gross reserves for unpaid losses and loss adjustment expenses, end of period	$ 344,565	$ 284,428