Investments (Summary Of Changes In Net Unrealized Appreciation (Depreciation) For The Company's Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax	$ 55,587	$ 103,245	$ 392,640	$ 582,662
Deferred tax benefit (expense)	(3,560)	(9,984)	(44,116)	(62,415)
Deferred tax benefit (expense), other-than-temporary impairment		(25)		122
Total URA(D) on securities arising during the period	52,027	93,236	348,524	520,369
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax	55,587	103,173	392,640	584,333
Fixed Maturity Securities, Other-Than-Temporary Impairment [Member]
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax		$ 72		$ (1,671)