Securities (Summary Of Securities Available For Sale In Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	$ 121,088	$ 65,199
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,126)	(550)
12 months or more, Estimated Fair Value	28,875	37,384
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,031)	(964)
Total Estimated Fair Value	149,963	102,583
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3,157)	(1,514)
Temporarily Impaired Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	121,088	65,199
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,126)	(550)
12 months or more, Estimated Fair Value	28,875	37,384
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,031)	(964)
Total Estimated Fair Value	149,963	102,583
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3,157)	(1,514)
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	19,052	10,864
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(206)	(91)
12 months or more, Estimated Fair Value	2,199	2,394
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(49)	(54)
Total Estimated Fair Value	21,251	13,258
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(255)	(145)
Temporarily Impaired Securities [Member] | Government Sponsored Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	32,858	32,156
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(516)	(269)
12 months or more, Estimated Fair Value	18,412	22,584
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(715)	(634)
Total Estimated Fair Value	51,270	54,740
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1,231)	(903)
Temporarily Impaired Securities [Member] | Nongovernment Sponsored Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	218	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1)	0
12 months or more, Estimated Fair Value	677	810
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(4)	(7)
Total Estimated Fair Value	895	815
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(5)	(7)
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	5,904	6,035
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(184)	(55)
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	5,904	6,035
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(184)	(55)
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	12,351	7,532
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(283)	(62)
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	12,351	7,532
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(283)	(62)
Temporarily Impaired Securities [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value	964	3,008
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(36)	(39)
12 months or more, Estimated Fair Value	3,684	1,659
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(110)	(91)
Total Estimated Fair Value	4,648	4,667
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(146)	(130)
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	19,967	2,999
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(407)	(20)
12 months or more, Estimated Fair Value	3,903	9,937
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(153)	(178)
Total Estimated Fair Value	23,870	12,936
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(560)	(198)
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	5,990	282
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(94)	(3)
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	5,990	282
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(94)	(3)
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	2,234	569
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(22)	(2)
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	2,234	569
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(22)	(2)
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	2,261
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	2,261
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(41)
Temporarily Impaired Securities [Member] | Tax Exempt State and Political Subdivisions University Revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Estimated Fair Value		1,749
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(9)
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		1,749
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ (9)
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	19,289
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(336)
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	19,289
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (336)