Loss And Loss Adjustment Expense Reserves (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2019	Jun. 30, 2019	Jun. 30, 2018
Unusual or Infrequent Item, or Both [Line Items]
Prior year claims and claims adjustment expense		$ 10,758	$ 63,919
Adjustments for prior year claims		557,457	540,803
Catastrophe [Member]
Unusual or Infrequent Item, or Both [Line Items]
Loss from catastrophes, net of reinsurance benefits		14,000	$ 11,000
Loss from catastrophes		17,000
Adjustments for prior year claims		$ 3,000
Fire [Member]
Unusual or Infrequent Item, or Both [Line Items]
Loss from catastrophes, net of reinsurance benefits	$ 40,000
Loss from catastrophes	208,000
Benefit from sale of subrogation rights	$ 10,000