Investments (Amortized Cost And Estimated Fair Value Of Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Securities Available-for-Sale, Amortized Cost
Securities Available-for-Sale, Due in one year or less, Cost	$ 2,715
Securities Available-for-Sale, Due after one year through five years, Cost	13,888
Securities Available-for-Sale, Due after five years through ten years, Cost	76,197
Securities Available-for-Sale, Due after ten years, Cost	470,998
Securities Available-for-Sale, Cost, Total	563,798
Securities Available-for-Sale, Estimated Fair Value
Securities Available-for-Sale, Due in one year or less, Estimated Fair Value	2,715
Securities Available-for-Sale, Due after one year through five years, Estimated Fair Value	13,850
Securities Available-for-Sale, Due after five years through ten years, Estimated Fair Value	73,698
Securities Available-for-Sale, Due after ten years, Estimated Fair Value	458,604
Securities Available-for-Sale, Estimated Fair Value, Total	548,867
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	62,277
Securities Held-to-Maturity, Amortized Cost	62,277	$ 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	62,146
Securities Held-to-Maturity, Estimated Fair Value	$ 62,146	$ 65,646