Loss And Loss Adjustment Expense Reserves (Narrative) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Unusual or Infrequent Item, or Both [Line Items]
Prior years	$ 63,919	$ 14,152
Catastrophe [Member]
Unusual or Infrequent Item, or Both [Line Items]
Pre-tax catastrophe losses	$ 11,000	$ 40,000