Losses And Loss Adjustment Expense Reserves (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unusual or Infrequent Item, or Both [Line Items]
Prior year claims and claim adjustment expense	$ 54,431	$ 85,369	$ 12,658
Catastrophe [Member]
Unusual or Infrequent Item, or Both [Line Items]
Pre-tax catastrophe losses	168,000	$ 27,000	$ 19,000
Pre-tax catastrophe losses, net of reinsurance benefits	$ 79,000