Securities (Summary Of Amortized Cost, Unrealized Gains, Unrealized Losses And Estimated Fair Values) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	$ 267,105	$ 276,443
Available for sale securities, Unrealized Gains	3,005	5,576
Available for sale securities, Unrealized Losses	3,568	1,227
Available for sale securities, Estimated Fair Value	266,542	280,792
U.S. Government and agencies and corporations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	14,580	20,461
Available for sale securities, Unrealized Gains	642	1,063
Available for sale securities, Unrealized Losses	48	49
Available for sale securities, Estimated Fair Value	15,174	21,475
Government-sponsored agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	138,451	145,586
Available for sale securities, Unrealized Gains	1,554	1,943
Available for sale securities, Unrealized Losses	1,159	795
Available for sale securities, Estimated Fair Value	138,846	146,734
Nongovernment-sponsored entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	4,631	7,836
Available for sale securities, Unrealized Gains	44	82
Available for sale securities, Unrealized Losses	22	33
Available for sale securities, Estimated Fair Value	4,653	7,885
State and policital subdivisions, Water and sewer revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost		250
Available for sale securities, Unrealized Gains		0
Available for sale securities, Unrealized Losses		0
Available for sale securities, Estimated Fair Value		250
State and policital subdivisions, Other revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost		1,729
Available for sale securities, Unrealized Gains		0
Available for sale securities, Unrealized Losses		26
Available for sale securities, Estimated Fair Value		1,703
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	18,295	14,494
Available for sale securities, Unrealized Gains	23	0
Available for sale securities, Unrealized Losses	148	268
Available for sale securities, Estimated Fair Value	18,170	14,226
Total taxable debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	175,957	190,356
Available for sale securities, Unrealized Gains	2,263	3,088
Available for sale securities, Unrealized Losses	1,377	1,171
Available for sale securities, Estimated Fair Value	176,843	192,273
State and political subdivisions, General obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	49,449	52,490
Available for sale securities, Unrealized Gains	569	1,767
Available for sale securities, Unrealized Losses	1,388	41
Available for sale securities, Estimated Fair Value	48,630	54,216
State and political subdivisions, Water and sewer revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	9,087	7,614
Available for sale securities, Unrealized Gains	63	172
Available for sale securities, Unrealized Losses	149	0
Available for sale securities, Estimated Fair Value	9,001	7,786
State and political subdivisions, Lease revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	9,037	8,671
Available for sale securities, Unrealized Gains	7	187
Available for sale securities, Unrealized Losses	201	1
Available for sale securities, Estimated Fair Value	8,843	8,857
State and Political Subdivisions Special Tax Revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost		4,532
Available for sale securities, Unrealized Gains		72
Available for sale securities, Unrealized Losses		0
Available for sale securities, Estimated Fair Value		4,604
State and Political Subdivisions Electric Revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	3,247
Available for sale securities, Unrealized Gains	10
Available for sale securities, Unrealized Losses	48
Available for sale securities, Estimated Fair Value	3,209
State and Political Subdivisions Sales Tax Revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	2,870
Available for sale securities, Unrealized Gains	0
Available for sale securities, Unrealized Losses	34
Available for sale securities, Estimated Fair Value	2,836
State and political subdivisions, Other revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	17,321	12,703
Available for sale securities, Unrealized Gains	93	290
Available for sale securities, Unrealized Losses	371	14
Available for sale securities, Estimated Fair Value	17,043	12,979
Total tax-exempt debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	91,011	86,010
Available for sale securities, Unrealized Gains	742	2,488
Available for sale securities, Unrealized Losses	2,191	56
Available for sale securities, Estimated Fair Value	89,562	88,442
Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	137	77
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Unrealized Losses	0	0
Available for sale securities, Estimated Fair Value	$ 137	$ 77