Investments (Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities, By Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value		$ 2,495,611
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation		(113,584)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value		1,599,859
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation		(55,428)
Fixed maturity securities, Total, Market Value	$ 4,269,794	4,095,470
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(221,587)	(169,012)
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	2,819,476	2,445,326	$ 2,819,476
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(118,097)	(109,516)	(118,097)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	1,352,447	1,525,865	1,352,447
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(85,569)	(47,549)	(85,569)
Fixed maturity securities, Total, Market Value	4,171,923	3,971,191	4,171,923
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(203,666)	(157,065)	(203,666)
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	85,547	98,021
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(4,021)	(5,166)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	83,375	80,002
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(12,950)	(8,174)
Fixed maturity securities, Total, Market Value	168,922	178,023
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(16,971)	(13,340)
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	1,220,223	1,233,244
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(50,689)	(68,124)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	577,851	518,613
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(41,640)	(12,761)
Fixed maturity securities, Total, Market Value	1,798,074	1,751,857
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(92,329)	(80,885)
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	924,605	679,374
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(51,295)	(28,529)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	208,989	187,717
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(20,624)	(10,734)
Fixed maturity securities, Total, Market Value	1,133,594	867,091
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(71,919)	(39,263)
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	111,635	72,436
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(8,439)	(6,172)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	54,693	50,518
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(5,448)	(4,116)
Fixed maturity securities, Total, Market Value	166,328	122,954
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(13,887)	(10,288)
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	89,526	192,253	89,526
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(674)	(1,230)	(674)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	44,765		44,765
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(880)		(880)
Fixed maturity securities, Total, Market Value	134,291	192,253	134,291
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(1,554)	(1,230)	$ (1,554)
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	387,940	169,998
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(2,979)	(295)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	382,774	689,015
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(4,027)	(11,764)
Fixed maturity securities, Total, Market Value	770,714	859,013
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	$ (7,006)	$ (12,059)