Investments (Cost And Estimated Fair Value Of Investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Investments
Cost	$ 5,978	$ 2,034
Cash equivalents, Carrying amount	3,902	7,646
Gross unrealized gain	48	2
Gross unrealized loss	0	0
Fair value, investments	6,026	2,036
Money Market Savings [Member]
Investments
Cost	1,694
Gross unrealized gain	0
Gross unrealized loss	0
Fair value, investments	1,694
Commercial Paper [Member]
Investments
Cost		1,377
Gross unrealized gain		0
Gross unrealized loss		0
Fair value, investments		1,377
Treasury Bills [Member]
Investments
Cost	7,898	7,922
Gross unrealized gain	47	32
Gross unrealized loss	0	0
Fair value, investments	7,945	7,954
Equity Securities [Member]
Investments
Cost	54	54
Gross unrealized gain	2	2
Gross unrealized loss	0	0
Fair value, investments	56	56
Debt and Equity Securities [Member]
Investments
Cost	9,646	9,353
Gross unrealized gain	49	34
Gross unrealized loss	0	0
Fair value, investments	9,695	9,387
Less Cash Equivalents [Member]
Investments
Cash equivalents, Carrying amount	3,668	7,319
Gross unrealized gain	1	32
Gross unrealized loss	0	0
Cash equivalents, Fair value	$ 3,669	$ 7,351