Investments (Summary Of Components Of Net Realized Capital Gains (Losses)) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Total net realized capital gains (losses)	$ 38,902	$ (210,588)
Beginning Balance	(1,745)
Credit losses on securities where credit losses were not previously recorded	(7,298)	(21,774)
Increases in allowance on previously impaired securities
Decrease in allowance on previously impaired securities
Reduction in allowance due to disposals	320
Ending Balance	(8,723)	(21,774)
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance	(1,745)
Ending Balance	(8,723)
Fixed Maturity Securities [Member] \| Market Value [Member]
Schedule of Available-for-sale Securities [Line Items]
Allowance for credit losses	6,977	21,774
Gains (losses) from sales	9,174	(14,076)
Fixed Maturity Securities [Member] \| Fair Value [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from sales
Gains (losses) from fair value adjustments		(1,123)
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance	(1,220)
Credit losses on securities where credit losses were not previously recorded	(2,383)	(17,305)
Increases in allowance on previously impaired securities
Decrease in allowance on previously impaired securities
Reduction in allowance due to disposals
Ending Balance	(3,603)	(17,305)
Equity Securities [Member] \| Fair Value [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from sales	6,238	(27,599)
Gains (losses) from fair value adjustments	29,056	(144,003)
Other Invested Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from sales	1,346	(2,327)
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from sales	66	314
Asset Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance
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)
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance	(22)
Credit losses on securities where credit losses were not previously recorded		(519)
Increases in allowance on previously impaired securities
Decrease in allowance on previously impaired securities
Reduction in allowance due to disposals	22
Ending Balance		(519)
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance	(503)
Credit losses on securities where credit losses were not previously recorded		(3,950)
Increases in allowance on previously impaired securities
Decrease in allowance on previously impaired securities
Reduction in allowance due to disposals	298
Ending Balance	$ (205)	$ (3,950)

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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