Investments (Amortized Cost And Estimated Fair Value Of Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Securities Available-for-Sale, Amortized Cost
Securities Available-for-Sale, Due in one year or less, Cost	$ 2,685
Securities Available-for-Sale, Due after one year through five years, Cost	10,504
Securities Available-for-Sale, Due after five years through ten years, Cost	81,069
Securities Available-for-Sale, Due after ten years, Cost	490,906
Securities Available-for-Sale, Cost, Total	585,164
Securities Available-for-Sale, Estimated Fair Value
Securities Available-for-Sale, Due in one year or less, Estimated Fair Value	2,684
Securities Available-for-Sale, Due after one year through five years, Estimated Fair Value	10,493
Securities Available-for-Sale, Due after five years through ten years, Estimated Fair Value	76,996
Securities Available-for-Sale, Due after ten years, Estimated Fair Value	471,386
Securities Available-for-Sale, Estimated Fair Value, Total	561,559
Securities Held-to-Maturity, Amortized Cost
Securities Held-to-Maturity, Due in one year or less, Cost	0
Securities Held-to-Maturity, Due after one year through five years, Cost	0
Securities Held-to-Maturity, Due after five years through ten years, Cost	0
Securities Held-to-Maturity, Due after ten years, Cost	57,812
Securities Held-to-Maturity, Amortized Cost	57,812	$ 64,449
Securities Held-to-Maturity, Estimated Fair Value
Securities Held-to-Maturity, Due in one year or less, Estimated Fair Value	0
Securities Held-to-Maturity, Due after one year through five years, Estimated Fair Value	0
Securities Held-to-Maturity, Due after five years through ten years, Estimated Fair Value	0
Securities Held-to-Maturity, Due after ten years, Estimated Fair Value	56,841
Securities Held-to-Maturity, Estimated Fair Value	$ 56,841	$ 65,646