Investments In Securities (Schedule Of Unrealized Losses On Investments) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Total temporarily impaired securities, Less than 12 Months, Fair Value	$ 38,314	$ 22,897
Total temporarily impaired securities, Less than 12 Months, Unrealized Losses	(349)	(96)
Total temporarily impaired securities, 12 Months or Longer, Fair Value	7,842	7,558
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(319)	(127)
Total temporarily impaired securities, Total Fair Value	46,156	30,455
Total temporarily impaired securities, Unrealized Losses	(668)	(223)
Government obligations
Schedule of Available-for-sale Securities [Line Items]
Total temporarily impaired securities, Less than 12 Months, Fair Value		1,042
Total temporarily impaired securities, Less than 12 Months, Unrealized Losses		(1)
Total temporarily impaired securities, 12 Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Total temporarily impaired securities, Total Fair Value		1,042
Total temporarily impaired securities, Unrealized Losses		(1)
General Obligations Us States And Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total temporarily impaired securities, Less than 12 Months, Fair Value	9,120	4,560
Total temporarily impaired securities, Less than 12 Months, Unrealized Losses	(108)	(27)
Total temporarily impaired securities, 12 Months or Longer, Fair Value	3,430	3,535
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(119)	(23)
Total temporarily impaired securities, Total Fair Value	12,550	8,095
Total temporarily impaired securities, Unrealized Losses	(227)	(50)
Issuer Obligations Us States And Political Subdivisions Debt Securities Special Revenues [Member]
Schedule of Available-for-sale Securities [Line Items]
Total temporarily impaired securities, Less than 12 Months, Fair Value	18,979	13,551
Total temporarily impaired securities, Less than 12 Months, Unrealized Losses	(180)	(61)
Total temporarily impaired securities, 12 Months or Longer, Fair Value	4,412	4,023
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(200)	(104)
Total temporarily impaired securities, Total Fair Value	23,391	17,574
Total temporarily impaired securities, Unrealized Losses	(380)	(165)
Corporate Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Total temporarily impaired securities, Less than 12 Months, Fair Value	10,215	3,744
Total temporarily impaired securities, Less than 12 Months, Unrealized Losses	(61)	(7)
Total temporarily impaired securities, 12 Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total temporarily impaired securities, Total Fair Value	10,215	3,744
Total temporarily impaired securities, Unrealized Losses	(61)	(7)
Total Fixed Income Securities
Schedule of Available-for-sale Securities [Line Items]
Total temporarily impaired securities, Less than 12 Months, Fair Value	38,314	22,897
Total temporarily impaired securities, Less than 12 Months, Unrealized Losses	(349)	(96)
Total temporarily impaired securities, 12 Months or Longer, Fair Value	7,842	7,558
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(319)	(127)
Total temporarily impaired securities, Total Fair Value	46,156	30,455
Total temporarily impaired securities, Unrealized Losses	$ (668)	$ (223)