Investments (Summary Of Components Of Net Realized Capital Gains (Losses)) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Schedule of Available-for-sale Securities [Line Items]
Other invested assets	$ 2,748	$ 1,292	$ 4,094	$ (1,035)
Total net realized capital gains (losses)	183,763	(479,360)	318,774	(222,493)
Beginning Balance	(8,708)	(12,099)	(1,566)
Credit losses on securities where credit losses were not previously recorded	(13,726)	(10,355)	(21,024)	(22,454)
Increases in allowance on previously impaired securities	(1,468)	(766)	(1,468)	(766)
Decrease in allowance on previously impaired securities		1,354		1,354
Reduction in allowance due to disposals	119	1,941	275	1,941
Ending Balance	(23,783)	(19,925)	(23,783)	(19,925)
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance			(1,566)
Ending Balance	(23,783)		(23,783)
Fixed Maturity Securities [Member] \| Market Value [Member]
Schedule of Available-for-sale Securities [Line Items]
Allowance for credit losses	(15,075)	(7,826)	(22,217)	(19,925)
Gains (losses) from sales	4,128	1,963	8,055	(18,974)
Fixed Maturity Securities [Member] \| Fair Value [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from fair value adjustments		(272)		(1,395)
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance	(3,588)	(11,468)	(1,205)
Credit losses on securities where credit losses were not previously recorded	(13,538)	(10,355)	(15,921)	(21,823)
Increases in allowance on previously impaired securities	(1,468)	(555)	(1,468)	(555)
Decrease in allowance on previously impaired securities		1,238		1,238
Reduction in allowance due to disposals	119	1,742	119	1,742
Ending Balance	(18,475)	(19,398)	(18,475)	(19,398)
Asset Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance	(4,915)
Credit losses on securities where credit losses were not previously recorded			(4,915)
Increases in allowance on previously impaired securities
Decrease in allowance on previously impaired securities
Reduction in allowance due to disposals
Ending Balance	(4,915)		(4,915)
Equity Securities [Member] \| Fair Value [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from sales	585	16,274	6,823	(11,328)
Gains (losses) from fair value adjustments	103,824	148,205	141,375	26,536
Other Invested Assets [Member] \| Fair Value [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from fair value adjustments	87,552	(639,058)	180,630	(196,579)
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from sales	1	62	14	207
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance		(70)
Credit losses on securities where credit losses were not previously recorded				(70)
Increases in allowance on previously impaired securities
Decrease in allowance on previously impaired securities
Reduction in allowance due to disposals		70		70
Ending Balance
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance	(205)	(561)	(361)
Credit losses on securities where credit losses were not previously recorded	(188)		(188)	(561)
Increases in allowance on previously impaired securities		(211)		(211)
Decrease in allowance on previously impaired securities		116		116
Reduction in allowance due to disposals		129	156	129
Ending Balance	$ (393)	$ (527)	$ (393)	$ (527)

Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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