Reserves for Unpaid Losses and Loss Adjustment Expenses (Activity in the Reserves for Unpaid Losses and Loss Adjustment Expense) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Reserves for Unpaid Losses and Loss Adjustment Expenses [Abstract]
Balance at January 1	$ 527,100	$ 481,567
Less reinsurance recoverable	154,612	123,237
Net balance at January 1	372,488	358,330
Incurred related to:
Current year	185,506	184,685
Prior years	6,062	20,240
Total incurred	191,568	204,925
Paid related to:
Current year	56,687	61,288
Prior years	184,337	128,329
Total paid	241,024	189,617
Net balance at September 30	323,032	373,638
Plus reinsurance recoverable	207,784	157,861
Balance at September 30	$ 530,816	$ 531,499