Investments (Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities, By Security Type) (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)
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	81,465
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(106)
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	81,465
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(106)
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	20,473	19,524
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(214)	(999)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	3,189	4,059
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(772)	(256)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	23,662	23,583
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(986)	(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	760,710	240,601
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(21,706)	(7,799)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	83,158	188,853
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(1,533)	(23,681)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	843,868	429,454
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(23,239)	(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	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)
Commercial [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	108,610	37,414
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(2,478)	(182)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value		3,983
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation		(1)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	108,610	41,397
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(2,478)	(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	603,966	235,809
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(6,118)	(682)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	10,242	1,573
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(50)	(14)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	614,208	237,382
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(6,168)	(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		161
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation		(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	156	161
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(2)	(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	88,608	10,505
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(2,570)	(373)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	1,009	25,793
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(1)	(2,838)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	89,617	36,298
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(2,571)	(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	231,115	57,900
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(3,741)	(2,182)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	10,755	18,349
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(858)	(1,721)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	241,870	76,249
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	$ (4,600)	$ (3,903)