Investments (Amortized Cost And Estimated Fair Value Of Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Securities Available-for-Sale, Amortized Cost
Securities Available-for-Sale, Due in one year or less, Cost	$ 2,939
Securities Available-for-Sale, Due after one year through five years, Cost	12,388
Securities Available-for-Sale, Due after five years through ten years, Cost	80,329
Securities Available-for-Sale, Due after ten years, Cost	424,811
Securities Available-for-Sale, Cost, Total	520,467
Securities Available-for-Sale, Estimated Fair Value
Securities Available-for-Sale, Due in one year or less, Estimated Fair Value	2,951
Securities Available-for-Sale, Due after one year through five years, Estimated Fair Value	14,839
Securities Available-for-Sale, Due after five years through ten years, Estimated Fair Value	77,039
Securities Available-for-Sale, Due after ten years, Estimated Fair Value	424,288
Securities Available-for-Sale, Estimated Fair Value, Total	519,117
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	66,989
Securities Held-to-Maturity, Amortized Cost	66,989	$ 75,169
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	68,478
Securities Held-to-Maturity, Estimated Fair Value	$ 68,478	$ 76,445