Investments In Securities and Fair Value (Schedule Of Unrealized Losses On Investments) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Government obligations
Debt Securities, Available-for-sale [Line Items]
Total temporarily impaired securities, Less than 12 Months, Fair Value		$ 12,045
Total temporarily impaired securities, Less than 12 Months, Unrealized Losses		(4)
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		12,045
Total temporarily impaired securities, Unrealized Losses		(4)
Special revenue issuer obligations of U.S. states, territories and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Total temporarily impaired securities, Less than 12 Months, Fair Value	$ 0	1,101
Total temporarily impaired securities, Less than 12 Months, Unrealized Losses	0	(17)
Total temporarily impaired securities, 12 Months or Longer, Fair Value	1,106	1,118
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(4)	(3)
Total temporarily impaired securities, Total Fair Value	1,106	2,219
Total temporarily impaired securities, Unrealized Losses	(4)	(20)
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Total temporarily impaired securities, Less than 12 Months, Fair Value		413
Total temporarily impaired securities, Less than 12 Months, Unrealized Losses		(5)
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		413
Total temporarily impaired securities, Unrealized Losses		(5)
Total temporarily impaired securities
Debt Securities, Available-for-sale [Line Items]
Total temporarily impaired securities, Less than 12 Months, Fair Value	0	13,559
Total temporarily impaired securities, Less than 12 Months, Unrealized Losses	0	(26)
Total temporarily impaired securities, 12 Months or Longer, Fair Value	1,106	1,118
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(4)	(3)
Total temporarily impaired securities, Total Fair Value	1,106	14,677
Total temporarily impaired securities, Unrealized Losses	$ (4)	$ (29)