Securities (Summary Of Securities Available For Sale In Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	$ 107,577	$ 115,357
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,914)	(3,212)
12 months or more, Estimated Fair Value	11,632	17,113
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(300)	(356)
Total Estimated Fair Value	119,209	132,470
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2,214)	(3,568)
Temporarily Impaired Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	107,577	115,357
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,914)	(3,212)
12 months or more, Estimated Fair Value	11,632	17,113
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(300)	(356)
Total Estimated Fair Value	119,209	132,470
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2,214)	(3,568)
Temporarily Impaired Securities [Member] | U S Government Corporations And Agencies Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	5,486	763
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(28)	(5)
12 months or more, Estimated Fair Value	2,821	2,575
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(52)	(43)
Total Estimated Fair Value	8,307	3,338
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(80)	(48)
Temporarily Impaired Securities [Member] | Government Sponsored Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	46,724	55,388
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(736)	(985)
12 months or more, Estimated Fair Value	5,689	8,389
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(123)	(174)
Total Estimated Fair Value	52,413	63,777
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(859)	(1,159)
Temporarily Impaired Securities [Member] | Nongovernment Sponsored Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	0	97
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
12 months or more, Estimated Fair Value	1,354	3,013
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(11)	(22)
Total Estimated Fair Value	1,354	3,110
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(11)	(22)
Temporarily Impaired Securities [Member] | State and Political Subdivisions General Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	1,870
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(7)
12 months or more, Estimated Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Total Estimated Fair Value	1,870
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(7)
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	7,991
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(36)
12 months or more, Estimated Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Total Estimated Fair Value	7,991
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(36)
Temporarily Impaired Securities [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	2,975	968
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(82)	(31)
12 months or more, Estimated Fair Value	710	3,136
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(39)	(117)
Total Estimated Fair Value	3,685	4,104
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(121)	(148)
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	24,456	33,115
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(661)	(1,388)
12 months or more, Estimated Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total Estimated Fair Value	24,456	33,115
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(661)	(1,388)
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	5,295	4,761
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(102)	(149)
12 months or more, Estimated Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total Estimated Fair Value	5,295	4,761
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(102)	(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	1,684	7,011
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(27)	(201)
12 months or more, Estimated Fair Value	1,058	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(75)	0
Total Estimated Fair Value	2,742	7,011
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(102)	(201)
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	1,982	1,973
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(24)	(48)
12 months or more, Estimated Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total Estimated Fair Value	1,982	1,973
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(24)	(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	1,162	2,836
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(14)	(34)
12 months or more, Estimated Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total Estimated Fair Value	1,162	2,836
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(14)	(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	7,952	8,445
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(197)	(371)
12 months or more, Estimated Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total Estimated Fair Value	7,952	8,445
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (197)	$ (371)