Investments (Summary Of Amortized Cost And Market Value Of Fixed Maturity Securities, By Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 13,754,572	$ 12,733,499
Fair Value	12,873,421	12,860,395
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	550,584	586,432
Fixed maturity securities - available for sale, Due after one year through five years, Amortized Cost	3,688,680	3,488,358
Fixed maturity securities - available for sale, Due after five years through ten years, Amortized Cost	2,134,269	2,260,481
Fixed maturity securities - available for sale, Due after ten years, Amortized Cost	1,360,431	1,087,955
Amortized Cost	13,754,572	12,733,499
Fixed maturity securities - available for sale, Due in one year or less, Market Value	545,751	583,676
Fixed maturity securities - available for sale, Due after one year through five years, Market Value	3,513,385	3,526,854
Fixed maturity securities - available for sale, Due after five years through ten years, Market Value	1,933,772	2,309,870
Fixed maturity securities - available for sale, Due after ten years, Market Value	1,191,431	1,105,729
Fair Value	12,873,421	12,860,395
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,928,582	3,464,248
Fair Value	3,751,371	3,466,286
Commercial [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	566,417	586,441
Fair Value	524,418	602,894
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,522,073	1,255,186
Fair Value	1,409,900	1,260,678
Non-agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,536	4,398
Fair Value	$ 3,393	$ 4,408

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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