Investments (Cost And Estimated Fair Value Of Investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 5,730	$ 7,701
Gross unrealized gain	56	41
Gross unrealized loss	0	0
Fair value, investments	5,786	7,742
Cash equivalents, Carrying amount	3,117	1,057	$ 853	$ 963
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	810	667
Gross unrealized gain	0	0
Gross unrealized loss	0	0
Fair value, investments	810	667
Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	7,684	7,656
Gross unrealized gain	56	41
Gross unrealized loss	0	0
Fair value, investments	7,740	7,697
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	45	45
Gross unrealized gain	0	0
Gross unrealized loss	0	0
Fair value, investments	45	45
Debt and Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	8,539	8,368
Gross unrealized gain	56	41
Gross unrealized loss	0	0
Fair value, investments	8,595	8,409
Less Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gain	0	0
Gross unrealized loss	0	0
Cash equivalents, Carrying amount	2,809	667
Cash equivalents, Fair value	$ 2,809	$ 667