Investments (Summary Of Changes In Net Unrealized Appreciation (Depreciation) For The Company's Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax	$ 311,927	$ 93,551	$ 123,520	$ 204,128
Deferred tax benefit (expense)	(64,834)	(19,675)	(26,065)	(42,889)
Deferred tax benefit (expense), other-than-temporary impairment		77		147
Total URA(D) on securities arising during the period	247,093	73,953	97,455	161,386
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax	311,927	93,919	123,520	204,828
Fixed Maturity Securities, Other-Than-Temporary Impairment [Member]
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax		$ (368)		$ (700)