Investments (Amortized Cost And Estimated Fair Value Of Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investments [Abstract]
Securities Available-for-Sale, Due in one year or less, Cost	$ 3,002
Securities Available-for-Sale, Due after one year through five years, Cost	15,824
Securities Available-for-Sale, Due after five years through ten years, Cost	76,555
Securities Available-for-Sale, Due after ten years, Cost	452,061
Securities Available-for-Sale, Cost, Total	547,442
Securities Available-for-Sale, Due in one year or less, Estimated Fair Value	3,005
Securities Available-for-Sale, Due after one year through five years, Estimated Fair Value	15,854
Securities Available-for-Sale, Due after five years through ten years, Estimated Fair Value	75,450
Securities Available-for-Sale, Due after ten years, Estimated Fair Value	448,892
Securities Available-for-Sale, Estimated Fair Value, Total	543,201
Securities Held-to-Maturity, Due after ten years, Cost	64,449
Securities Held-to-Maturity, Cost, Total	64,449	$ 75,169
Securities Held-to-Maturity, Due after ten years, Estimated Fair Value	65,646
Securities held-to-maturity, Estimated Fair Value	$ 65,646	$ 76,445