Investments (Amortized Cost And Estimated Fair Value Of Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Amortized Cost
Due in one year or less	$ 3,829
Due after one year through five years	42,608
Due after five years through ten years	248,098
Due after ten years	1,052,962
Total	1,347,497	$ 1,128,163
Estimated Fair Value
Due in one year or less	3,888
Due after one year through five years	44,755
Due after five years through ten years	259,506
Due after ten years	1,063,928
Total	$ 1,372,077	$ 1,176,797