Loss And Loss Adjustment Expense Reserves (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Unusual or Infrequent Item, or Both [Line Items]
Prior year claims and claims adjustment expense	$ 15,104	$ 1,362
Adjustments for prior year claims	403,436	344,718
Catastrophe [Member]
Unusual or Infrequent Item, or Both [Line Items]
Liability for catastrophe claims, net of reinsurance benefits	2,000	5,000
Adjustments for prior year claims	2,000	6,000
Liability for catastrophe claims, carrying amount	$ 4,000	11,000
Fire [Member]
Unusual or Infrequent Item, or Both [Line Items]
Loss from catastrophes, net of reinsurance benefits		40,000
Liability for catastrophe claims, carrying amount		208,000
Benefit from sale of subrogation rights		$ 10,000