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Investments (Summary Of Components Of Net Realized Capital Gains (Losses)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Other-than-temporary impairments										$ (20,899)	$ (8,110)
Total net realized capital gains (losses)	$ 183,386	$ 110,203	$ 184,648	$ (210,588)	$ 75,443	$ (12,943)	$ 30,272	$ 92,232	267,649	185,004	(127,136)
Beginning Balance
Credit losses on securities where credit losses were not previously recorded									(32,884)
Increases in allowance on previously impaired securities									(6,645)
Decrease in allowance on previously impaired securities									5,525
Reduction in allowance due to disposals									32,259
Ending Balance	(1,745)								(1,745)
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Ending Balance	(1,745)								(1,745)
Fixed Maturity Securities [Member] \| Market Value [Member]
Schedule of Available-for-sale Securities [Line Items]
Allowance for credit losses									(1,745)
Other-than-temporary impairments										(20,899)	(8,110)
Gains (losses) from sales									(2,214)	28,025	(21,719)
Fixed Maturity Securities [Member] \| Fair Value [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from sales									(2,863)	355	(1,799)
Gains (losses) from fair value adjustments									1,944	1,808	1,506
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance
Credit losses on securities where credit losses were not previously recorded									(27,666)
Increases in allowance on previously impaired securities									(6,136)
Decrease in allowance on previously impaired securities									4,333
Reduction in allowance due to disposals									28,249
Ending Balance	(1,220)								(1,220)
Equity Securities [Member] \| Fair Value [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from sales									(8,963)	4,148	(29,941)
Gains (losses) from fair value adjustments									278,461	165,200	(68,832)
Other Invested Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from sales									1,705	6,003	1,815
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) from sales									1,324	364	$ (56)
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance
Credit losses on securities where credit losses were not previously recorded									(518)
Increases in allowance on previously impaired securities									(28)
Decrease in allowance on previously impaired securities									309
Reduction in allowance due to disposals									215
Ending Balance	(22)								(22)
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Beginning Balance
Credit losses on securities where credit losses were not previously recorded									(4,700)
Increases in allowance on previously impaired securities									(481)
Decrease in allowance on previously impaired securities									883
Reduction in allowance due to disposals									3,795
Ending Balance	$ (503)								$ (503)