Investments (Summary Of Amortized Cost And Market Value Of Fixed Maturity Securities, By Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	$ 6,838,605	$ 7,032,749
Fixed maturity securities - available for sale, Market Value	6,971,971	6,962,075
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Due in one year or less, Amortized Cost	637,109	511,193
Fixed maturity securities - available for sale, Due after one year through five years, Amortized Cost	2,922,404	4,271,245
Fixed maturity securities - available for sale, Due after five years through ten years, Amortized Cost	1,294,439	1,177,752
Fixed maturity securities - available for sale, Due after ten years, Amortized Cost	591,018	561,566
Fixed maturity securities - available for sale, Due in one year or less, Market Value	631,917	507,572
Fixed maturity securities - available for sale, Due after one year through five years, Market Value	2,955,499	4,230,451
Fixed maturity securities - available for sale, Due after five years through ten years, Market Value	1,348,170	1,163,831
Fixed maturity securities - available for sale, Due after ten years, Market Value	613,272	550,474
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	516,941	223,192
Fixed maturity securities - available for sale, Market Value	517,207	221,255
Commercial [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	271,298	135,380
Fixed maturity securities - available for sale, Market Value	286,611	136,604
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	602,695	149,306
Fixed maturity securities - available for sale, Market Value	616,591	148,774
Non-agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	2,701	3,115
Fixed maturity securities - available for sale, Market Value	$ 2,704	$ 3,114

Amount of debt securities categorized neither as held-to-maturity nor trading, held at market value.

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