Reserves for Unpaid Losses and Loss Adjustment Expenses (Activity in the Reserves for Unpaid Losses and Loss Adjustment Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 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	64,205	62,331
Prior years	(530)	(489)
Total incurred	63,675	61,842
Paid related to:
Current year	13,829	12,583
Prior years	72,432	47,533
Total paid	86,261	60,116
Net balance at March 31	529,684	486,971
Plus reinsurance recoverable	179,782	126,915
Balance at March 31	$ 349,902	$ 360,056