Loss And Loss Adjustment Expense Reserves (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Unusual or Infrequent Item, or Both [Line Items]
Prior years		$ (26,091)	$ 22,979	$ 9,794
Prior year claims and claim adjustment expense payments		909,949	937,143	857,872
Catastrophe
Unusual or Infrequent Item, or Both [Line Items]
Prior years		(26,100)	23,000	9,800
Pre-tax catastrophe losses, net of reinsurance benefits		104,000	64,000	53,000
Pre-tax catastrophe losses		109,000	69,000	57,000
Prior year claims and claim adjustment expense payments		$ 5,000	$ 5,000	$ 4,000
Fire
Unusual or Infrequent Item, or Both [Line Items]
Loss from catastrophes	$ 208,000
Loss from catastrophes, net of reinsurance benefits	40,000
Salvage and subrogation recoveries, value	$ 10,000