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, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Market Value, Total	$ 1,469,577	$ 1,540,376
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(90,409)	(45,484)
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	1,129,113	759,174
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(43,687)	(8,539)
Available for sale securities, Greater than 12 months, Market Value	340,464	781,202
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(46,722)	(36,945)
Available-for-sale Securities, Market Value, Total	1,469,577	1,540,376
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(90,409)	(45,484)
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value		8,997
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation		(141)
Available for sale securities, Greater than 12 months, Market Value		203,780
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation		(846)
Available-for-sale Securities, Market Value, Total		212,777
Available-for-sale Securities, Gross Unrealized Depreciation, Total		(987)
Obligation of U.S. States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	70,056	4,600
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(3,564)	(38)
Available for sale securities, Greater than 12 months, Market Value	3,331	4,518
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(225)	(49)
Available-for-sale Securities, Market Value, Total	73,387	9,118
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(3,789)	(87)
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	423,967	334,973
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(20,116)	(5,186)
Available for sale securities, Greater than 12 months, Market Value	122,165	230,679
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(31,806)	(21,252)
Available-for-sale Securities, Market Value, Total	546,132	565,652
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(51,922)	(26,438)
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	437,211	159,695
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(16,250)	(887)
Available for sale securities, Greater than 12 months, Market Value	129,870	76,351
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(5,250)	(422)
Available-for-sale Securities, Market Value, Total	567,081	236,046
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(21,500)	(1,309)
Commercial [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	31,984	13,083
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(756)	(87)
Available for sale securities, Greater than 12 months, Market Value	3,303	16,374
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(32)	(67)
Available-for-sale Securities, Market Value, Total	35,287	29,457
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(788)	(154)
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	23,621	19,019
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(342)	(82)
Available for sale securities, Greater than 12 months, Market Value	1,166	17,147
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(7)	(238)
Available-for-sale Securities, Market Value, Total	24,787	36,166
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(349)	(320)
Non-agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	161
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(2)
Available for sale securities, Greater than 12 months, Market Value	344	690
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(1)
Available-for-sale Securities, Market Value, Total	505	690
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(3)
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	51,453	113,256
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(506)	(858)
Available for sale securities, Greater than 12 months, Market Value	41,802	109,953
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(4,528)	(6,192)
Available-for-sale Securities, Market Value, Total	93,255	223,209
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(5,034)	(7,050)
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	90,660	105,551
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(2,151)	(1,260)
Available for sale securities, Greater than 12 months, Market Value	38,483	121,710
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(4,873)	(7,879)
Available-for-sale Securities, Market Value, Total	129,143	227,261
Available-for-sale Securities, Gross Unrealized Depreciation, Total	$ (7,024)	$ (9,139)