Investments (Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities, By Contractual Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value		$ 1,150,395
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total		(45,952)
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	$ 2,098,023	825,833
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(48,051)	(16,792)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	272,017	324,562
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(23,541)	(29,160)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	2,370,040	1,150,395
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(71,592)	(45,952)
Due In One Year Or Less [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	45,431	28,802
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(823)	(1,218)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	27,415	34,555
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(3,064)	(4,142)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	72,846	63,357
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(3,887)	(5,360)
Due In One Year Through Five Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	434,857	150,106
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(7,796)	(5,828)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	112,809	116,987
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(3,662)	(4,783)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	547,666	267,093
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(11,458)	(10,611)
Due In Five Years Through Ten Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	544,227	81,492
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(18,240)	(1,634)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	9,671	13,118
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(658)	(435)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	553,898	94,610
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(18,898)	(2,069)
Due After Ten Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	178,828	68,130
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(6,285)	(2,673)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	87,181	72,394
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(15,541)	(19,136)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	266,009	140,524
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(21,826)	(21,809)
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	240,987	223,919
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(1,749)	(4,573)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	22,773	81,952
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(461)	(649)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	263,760	305,871
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(2,210)	(5,222)
Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	653,693	273,384
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(13,158)	(866)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	12,168	5,556
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(155)	(15)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	665,861	278,940
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	$ (13,313)	$ (881)