Investments (Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities, By Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 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	$ 2,535,102	825,833
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(39,132)	(16,792)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	117,048	324,562
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(3,442)	(29,160)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	2,652,150	1,150,395
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(42,574)	(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	71,420	28,802
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(1,509)	(1,218)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	1,009	34,555
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(1)	(4,142)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	72,429	63,357
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(1,510)	(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	494,028	150,106
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(8,866)	(5,828)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	82,946	116,987
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(1,288)	(4,783)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	576,974	267,093
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(10,154)	(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	406,678	81,492
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(9,302)	(1,634)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	10,967	13,118
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(1,103)	(435)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	417,645	94,610
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(10,405)	(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	210,245	68,130
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(8,660)	(2,673)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	3,189	72,394
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(772)	(19,136)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	213,434	140,524
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(9,432)	(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	640,155	223,919
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(2,199)	(4,573)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	8,539	81,952
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(227)	(649)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	648,694	305,871
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(2,426)	(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	712,576	273,384
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(8,596)	(866)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	10,398	5,556
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(51)	(15)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	722,974	278,940
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	$ (8,647)	$ (881)