Reserves for Unpaid Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 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	96,673	87,365
Prior years	(5,722)	(11,831)
Total net losses and loss adjustment expenses incurred	90,951	75,534
Payments:
Current year	4,095	4,317
Prior years	52,056	28,763
Total payments	56,151	33,080
Net reserves for unpaid losses and loss adjustment expenses, end of period	302,293	264,985
Reinsurance recoverable on unpaid losses	63,521	45,949
Gross reserves for unpaid losses and loss adjustment expenses, end of period	$ 365,814	$ 310,934