Losses And Loss Adjustment Expense Reserves (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Unusual or Infrequent Item, or Both [Line Items]
Prior years claims and claim adjustment expense	$ 42,652	$ 4,124
Catastrophe [Member]
Unusual or Infrequent Item, or Both [Line Items]
Pre-tax catastrophe losses	$ 9,000	$ 30,000