Securities (Summary Of Securities Available For Sale In Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	$ 115,357	$ 75,212
Less than 12 months, Unrealized Loss	(3,212)	(921)
12 months or more, Estimated Fair Value	17,113	14,642
12 months or more, Unrealized Loss	(356)	(306)
Total Estimated Fair Value	132,470	89,854
Total Unrealized Loss	(3,568)	(1,227)
Temporarily Impaired Securities Member
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	115,357	75,212
Less than 12 months, Unrealized Loss	(3,212)	(921)
12 months or more, Estimated Fair Value	17,113	14,642
12 months or more, Unrealized Loss	(356)	(306)
Total Estimated Fair Value	132,470	89,854
Total Unrealized Loss	(3,568)	(1,227)
Temporarily Impaired Securities Member | U.S. Government and agencies and corporations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	763	2,104
Less than 12 months, Unrealized Loss	(5)	(2)
12 months or more, Estimated Fair Value	2,575	3,151
12 months or more, Unrealized Loss	(43)	(47)
Total Estimated Fair Value	3,338	5,255
Total Unrealized Loss	(48)	(49)
Temporarily Impaired Securities Member | Government-sponsored agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	55,388	52,970
Less than 12 months, Unrealized Loss	(985)	(569)
12 months or more, Estimated Fair Value	8,389	8,672
12 months or more, Unrealized Loss	(174)	(226)
Total Estimated Fair Value	63,777	61,642
Total Unrealized Loss	(1,159)	(795)
Temporarily Impaired Securities Member | Nongovernment-sponsored entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	97	2,298
Less than 12 months, Unrealized Loss	0	0
12 months or more, Estimated Fair Value	3,013	2,819
12 months or more, Unrealized Loss	(22)	(33)
Total Estimated Fair Value	3,110	5,117
Total Unrealized Loss	(22)	(33)
Temporarily Impaired Securities Member | State and political subdivisions, Other revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value		1,702
Less than 12 months, Unrealized Loss		(26)
12 months or more, Estimated Fair Value		0
12 months or more, Unrealized Loss		0
Total Estimated Fair Value		1,702
Total Unrealized Loss		(26)
Temporarily Impaired Securities Member | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	968	8,367
Less than 12 months, Unrealized Loss	(31)	(268)
12 months or more, Estimated Fair Value	3,136	0
12 months or more, Unrealized Loss	(117)	0
Total Estimated Fair Value	4,104	8,367
Total Unrealized Loss	(148)	(268)
Temporarily Impaired Securities Member | Tax Exempt State and Political Subdivisions General Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	33,115	5,977
Less than 12 months, Unrealized Loss	(1,388)	(41)
12 months or more, Estimated Fair Value	0	0
12 months or more, Unrealized Loss	0	0
Total Estimated Fair Value	33,115	5,977
Total Unrealized Loss	(1,388)	(41)
Temporarily Impaired Securities Member | Tax Exempt State and Political Subdivisions Water and Sewer Revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	4,761
Less than 12 months, Unrealized Loss	(149)
12 months or more, Estimated Fair Value	0
12 months or more, Unrealized Loss	0
Total Estimated Fair Value	4,761
Total Unrealized Loss	(149)
Temporarily Impaired Securities Member | Tax Exempt State and Political Subdivisions Lease Revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	7,011	576
Less than 12 months, Unrealized Loss	(201)	(1)
12 months or more, Estimated Fair Value	0	0
12 months or more, Unrealized Loss	0	0
Total Estimated Fair Value	7,011	576
Total Unrealized Loss	(201)	(1)
Temporarily Impaired Securities Member | Tax Exempt State and Political Subdivisions Electric Revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	1,973
Less than 12 months, Unrealized Loss	(48)
12 months or more, Estimated Fair Value	0
12 months or more, Unrealized Loss	0
Total Estimated Fair Value	1,973
Total Unrealized Loss	(48)
Temporarily Impaired Securities Member | Tax Exempt State and Political Subdivisions Sales Tax Revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	2,836
Less than 12 months, Unrealized Loss	(34)
12 months or more, Estimated Fair Value	0
12 months or more, Unrealized Loss	0
Total Estimated Fair Value	2,836
Total Unrealized Loss	(34)
Temporarily Impaired Securities Member | Tax Exempt State and Political Subdivisions Other Revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	8,445	1,218
Less than 12 months, Unrealized Loss	(371)	(14)
12 months or more, Estimated Fair Value	0	0
12 months or more, Unrealized Loss	0	0
Total Estimated Fair Value	8,445	1,218
Total Unrealized Loss	$ (371)	$ (14)