Investments (Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities, By Security Type) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	$ 2,885,334	$ 825,833
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(35,723)	(16,792)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	314,199	324,562
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(11,050)	(29,160)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	3,199,533	1,150,395
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(46,773)	(45,952)
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	164,510
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(911)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	164,510
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(911)
Obligation of U.S. States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	61,687	19,524
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(937)	(999)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	3,569	4,059
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(120)	(256)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	65,256	23,583
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(1,057)	(1,255)
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	926,023	240,601
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(15,559)	(7,799)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	171,444	188,853
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(5,456)	(23,681)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	1,097,467	429,454
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(21,015)	(31,480)
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	579,799	223,919
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(2,619)	(4,573)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	23,396	81,952
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(368)	(649)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	603,195	305,871
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(2,987)	(5,222)
Commercial [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	82,124	37,414
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(1,908)	(182)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	25,450	3,983
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(1,188)	(1)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	107,574	41,397
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(3,096)	(183)
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	459,632	235,809
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(2,872)	(682)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	55,358	1,573
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(651)	(14)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	514,990	237,382
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(3,523)	(696)
Non-agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	1,724	161
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(2)	(2)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	156
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(2)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	1,880	161
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(4)	(2)
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	178,925	10,505
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(2,881)	(373)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	10,819	25,793
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(1,866)	(2,838)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	189,744	36,298
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(4,747)	(3,211)
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	430,909	57,900
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(8,034)	(2,182)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	24,008	18,349
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(1,399)	(1,721)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	454,917	76,249
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	$ (9,433)	$ (3,903)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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