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	$ 614,077	$ 225,767	$ 337,053	$ 479,417
Deferred tax benefit (expense)	(69,581)	(29,954)	(40,557)	(52,431)
Deferred tax benefit (expense), other-than-temporary impairment		77		147
Total URA(D) on securities arising during the period	544,496	195,890	296,496	427,133
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax	614,077	227,266	337,053	481,160
Fixed Maturity Securities, Other-Than-Temporary Impairment [Member]
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax		$ (1,499)		$ (1,743)