Investments (Cost And Estimated Fair Value Of Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 54	$ 2,034
Gross unrealized gain	2	2
Gross unrealized loss	0	0
Fair value	56	2,036
Less cash equivalents, Carrying amount	9,870	7,646
Money Market [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	1,902
Gross unrealized gain	0
Gross unrealized loss	0
Fair value	1,902
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost		1,377
Gross unrealized gain		0
Gross unrealized loss		0
Fair value		1,377
Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	7,900	7,922
Gross unrealized gain	26	32
Gross unrealized loss	0	0
Fair value	7,926	7,954
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	54	54
Gross unrealized gain	2	2
Gross unrealized loss	0	0
Fair value	56	56
Debt and Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	9,856	9,353
Gross unrealized gain	28	34
Gross unrealized loss	0	0
Fair value	9,884	9,387
Less Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gain	26	32
Gross unrealized loss	0	0
Less cash equivalents, Carrying amount	9,802	7,319
Less cash equivalents, Fair value	$ 9,828	$ 7,351