Investments (Schedule Of Amortized Cost And Estimated Fair Value Of Fixed Maturity Securities By Contractual Maturity Date) (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, amortized cost	$ 1,486,434
Due after one year through five years, amortized cost	5,577,381
Due after five years through ten years, amortized cost	4,992,655
Due after ten years, amortized cost	1,348,502
Amortized cost, sub-total	13,404,972
Total fixed maturity securities, amortized cost	16,265,743	$ 14,932,286
Due in one year or less, estimated fair value	1,478,425
Due after one year through five years, estimated fair value	5,559,647
Due after five years through ten years, estimated fair value	4,971,587
Due after ten years, estimated fair value	1,261,285
Estimated fair value, sub-total	13,270,944
Total fixed maturity securities, estimated fair value	16,067,848	14,372,732
Agency mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	2,738,131
Total fixed maturity securities, amortized cost	2,738,131	2,507,682
Fixed maturity securities, estimated fair value	2,677,680
Total fixed maturity securities, estimated fair value	2,677,680	2,381,010
Non-agency mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities, amortized cost	122,640
Total fixed maturity securities, amortized cost	122,640	355,673
Fixed maturity securities, estimated fair value	119,224
Total fixed maturity securities, estimated fair value	$ 119,224	$ 333,070