Investments (Amortized Cost And Estimated Fair Value Of Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Securities Available-for-Sale, Amortized Cost
Securities Available-for-Sale, Due in one year or less, Cost	$ 2,861
Securities Available-for-Sale, Due after one year through five years, Cost	10,933
Securities Available-for-Sale, Due after five years through ten years, Cost	76,575
Securities Available-for-Sale, Due after ten years, Cost	478,759
Securities Available-for-Sale, Cost, Total	569,128
Securities Available-for-Sale, Estimated Fair Value
Securities Available-for-Sale, Due in one year or less, Estimated Fair Value	2,863
Securities Available-for-Sale, Due after one year through five years, Estimated Fair Value	10,954
Securities Available-for-Sale, Due after five years through ten years, Estimated Fair Value	73,198
Securities Available-for-Sale, Due after ten years, Estimated Fair Value	464,133
Securities Available-for-Sale, Estimated Fair Value, Total	551,148
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	60,030
Securities Held-to-Maturity, Amortized Cost	60,030	$ 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	59,628
Securities Held-to-Maturity, Estimated Fair Value	$ 59,628	$ 65,646