Securities (Summary Of Securities Available For Sale In Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	$ 121,104	$ 115,357
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3,008)	(3,212)
12 months or more, Estimated Fair Value	15,305	17,113
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(323)	(356)
Total Estimated Fair Value	136,409	132,470
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3,331)	(3,568)
Temporarily Impaired Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	121,104	115,357
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3,008)	(3,212)
12 months or more, Estimated Fair Value	15,305	17,113
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(323)	(356)
Total Estimated Fair Value	136,409	132,470
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3,331)	(3,568)
Temporarily Impaired Securities [Member] | Tax Exempt State and Political Subdivisions Transit Revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	1,118
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(41)
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	1,118
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(41)
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	0	763
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(5)
12 months or more, Estimated Fair Value	3,091	2,575
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(55)	(43)
Total Estimated Fair Value	3,091	3,338
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(55)	(48)
Temporarily Impaired Securities [Member] | Government Sponsored Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	59,339	55,388
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,073)	(985)
12 months or more, Estimated Fair Value	9,015	8,389
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(204)	(174)
Total Estimated Fair Value	68,354	63,777
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1,277)	(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	1,636	3,013
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(16)	(22)
Total Estimated Fair Value	1,636	3,110
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(16)	(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	779
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(6)
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	779
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(6)
Temporarily Impaired Securities [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	955	968
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(45)	(31)
12 months or more, Estimated Fair Value	1,563	3,136
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(48)	(117)
Total Estimated Fair Value	2,518	4,104
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(93)	(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	33,618	33,115
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,174)	(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	33,618	33,115
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1,174)	(1,388)
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	11,394	8,445
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(333)	(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	11,394	8,445
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(333)	(371)
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	2,196
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	2,196
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(7)
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	4,390	7,011
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(167)	(201)
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	4,390	7,011
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(167)	(201)
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	5,376	4,761
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(88)	(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	5,376	4,761
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(88)	(149)
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	1,939	1,973
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(74)	(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	1,939	1,973
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (74)	(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
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(34)
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		2,836
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ (34)