Securities (Summary Of Amortized Cost, Unrealized Gains, Unrealized Losses And Estimated Fair Values) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	$ 292,098	$ 324,908
Available for sale securities, Unrealized Gains	1,122	5,329
Available for sale securities, Unrealized Losses	5,180	1,514
Available for sale securities, Estimated Fair Value	288,040	328,723	[1]
U S Government Corporations And Agencies Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	27,504	31,260
Available for sale securities, Unrealized Gains	163	498
Available for sale securities, Unrealized Losses	388	145
Available for sale securities, Estimated Fair Value	27,279	31,613
Government Sponsored Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	73,931	120,948
Available for sale securities, Unrealized Gains	557	1,276
Available for sale securities, Unrealized Losses	1,546	903
Available for sale securities, Estimated Fair Value	72,942	121,321
Nongovernment Sponsored Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	682	2,045
Available for sale securities, Unrealized Gains	4	39
Available for sale securities, Unrealized Losses	1	7
Available for sale securities, Estimated Fair Value	685	2,077
State and Political Subdivisions General Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	6,084	6,090
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Unrealized Losses	266	55
Available for sale securities, Estimated Fair Value	5,818	6,035
State and Policital Subdivisions Other Revenues [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	13,462	11,657
Available for sale securities, Unrealized Gains	0	47
Available for sale securities, Unrealized Losses	506	62
Available for sale securities, Estimated Fair Value	12,956	11,642
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	11,914	16,375
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Unrealized Losses	227	130
Available for sale securities, Estimated Fair Value	11,687	16,245
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	21,861
Available for sale securities, Unrealized Gains	10
Available for sale securities, Unrealized Losses	79
Available for sale securities, Estimated Fair Value	21,792
Taxable Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	155,438	188,375
Available for sale securities, Unrealized Gains	734	1,860
Available for sale securities, Unrealized Losses	3,013	1,302
Available for sale securities, Estimated Fair Value	153,159	188,933
Tax Exempt State and Political Subdivisions General Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	72,299	65,560
Available for sale securities, Unrealized Gains	239	1,530
Available for sale securities, Unrealized Losses	1,200	198
Available for sale securities, Estimated Fair Value	71,338	66,892
Tax Exempt State and Political Subdivisions Water and Sewer Revenues [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	18,921	23,108
Available for sale securities, Unrealized Gains	75	566
Available for sale securities, Unrealized Losses	214	3
Available for sale securities, Estimated Fair Value	18,782	23,671
Tax Exempt State and Political Subdivisions Lease Revenues [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	13,305	13,024
Available for sale securities, Unrealized Gains	32	451
Available for sale securities, Unrealized Losses	57	2
Available for sale securities, Estimated Fair Value	13,280	13,473
Tax Exempt State and Political Subdivisions Electric Revenues [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	4,170	6,205
Available for sale securities, Unrealized Gains	15	128
Available for sale securities, Unrealized Losses	63	0
Available for sale securities, Estimated Fair Value	4,122	6,333
Tax Exempt State and Political Subdivisions Sales Tax Revenues [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost		4,126
Available for sale securities, Unrealized Gains		140
Available for sale securities, Unrealized Losses		0
Available for sale securities, Estimated Fair Value		4,266
Tax Exempt State and Political Subdivisions University Revenues [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost		5,272
Available for sale securities, Unrealized Gains		38
Available for sale securities, Unrealized Losses		9
Available for sale securities, Estimated Fair Value		5,301
Tax Exempt State and Political Subdivisions Other Revenues [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	27,828	19,101
Available for sale securities, Unrealized Gains	27	616
Available for sale securities, Unrealized Losses	633	0
Available for sale securities, Estimated Fair Value	27,222	19,717
Tax Exempt Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	136,523	136,396
Available for sale securities, Unrealized Gains	388	3,469
Available for sale securities, Unrealized Losses	2,167	212
Available for sale securities, Estimated Fair Value	134,744	139,653
Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	137	137
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Unrealized Losses	0	0
Available for sale securities, Estimated Fair Value	$ 137	$ 137

[1] Derived from audited consolidated financial statements